diff --git a/esphome/components/i2s_audio/__init__.py b/esphome/components/i2s_audio/__init__.py
index 6e4e35590c1..3d5ec97a633 100644
--- a/esphome/components/i2s_audio/__init__.py
+++ b/esphome/components/i2s_audio/__init__.py
@@ -19,8 +19,16 @@ from esphome.components.esp32.const import (
     VARIANT_ESP32S3,
 )
 from esphome.components.microphone import DOMAIN as MICROPHONE_DOMAIN
+from esphome.config_helpers import filter_source_files_from_defines
 import esphome.config_validation as cv
-from esphome.const import CONF_BITS_PER_SAMPLE, CONF_CHANNEL, CONF_ID, CONF_SAMPLE_RATE
+from esphome.const import (
+    CONF_BITS_PER_SAMPLE,
+    CONF_CHANNEL,
+    CONF_ID,
+    CONF_PLATFORM,
+    CONF_SAMPLE_RATE,
+    CONF_SPEAKER,
+)
 from esphome.core import CORE
 from esphome.cpp_generator import MockObj, MockObjClass
 import esphome.final_validate as fv
@@ -42,6 +50,9 @@ CONF_I2S_BCLK_PIN = "i2s_bclk_pin"
 CONF_I2S_LRCLK_PIN = "i2s_lrclk_pin"
 
 CONF_I2S_AUDIO_ID = "i2s_audio_id"
+CONF_FULL_DUPLEX = "full_duplex"
+CONF_I2S_COMM_FMT = "i2s_comm_fmt"
+CONF_SPDIF_MODE = "spdif_mode"
 
 CONF_I2S_MODE = "i2s_mode"
 CONF_PRIMARY = "primary"
@@ -185,7 +196,8 @@ def i2s_audio_component_schema(
 
 
 async def register_i2s_audio_component(var: MockObj, config: ConfigType) -> None:
-    await cg.register_parented(var, config[CONF_I2S_AUDIO_ID])
+    parent = await cg.get_variable(config[CONF_I2S_AUDIO_ID])
+    await cg.register_parented(var, parent)
     cg.add(var.set_i2s_role(I2S_ROLE_OPTIONS[config[CONF_I2S_MODE]]))
     slot_mode = config[CONF_CHANNEL]
     if slot_mode != CONF_STEREO:
@@ -200,6 +212,12 @@ async def register_i2s_audio_component(var: MockObj, config: ConfigType) -> None
     cg.add(var.set_use_apll(config[CONF_USE_APLL]))
     cg.add(var.set_mclk_multiple(I2S_MCLK_MULTIPLE[config[CONF_MCLK_MULTIPLE]]))
 
+    if str(config[CONF_I2S_AUDIO_ID]) in _get_data().full_duplex_buses:
+        if config[CONF_ID].type.inherits_from(I2SAudioIn):
+            cg.add(parent.set_audio_in(var))
+        else:
+            cg.add(parent.set_audio_out(var))
+
 
 CONFIG_SCHEMA = cv.Schema(
     {
@@ -207,6 +225,7 @@ CONFIG_SCHEMA = cv.Schema(
         cv.Optional(CONF_I2S_LRCLK_PIN): pins.internal_gpio_output_pin_number,
         cv.Optional(CONF_I2S_BCLK_PIN): pins.internal_gpio_output_pin_number,
         cv.Optional(CONF_I2S_MCLK_PIN): pins.internal_gpio_output_pin_number,
+        cv.Optional(CONF_FULL_DUPLEX, default=False): cv.boolean,
     },
 )
 
@@ -216,6 +235,7 @@ class I2SAudioData:
     """I2S audio component state stored in CORE.data."""
 
     port_map: dict[str, int] = field(default_factory=dict)
+    full_duplex_buses: set[str] = field(default_factory=set)
 
 
 def _get_data() -> I2SAudioData:
@@ -262,8 +282,56 @@ def _assign_ports() -> None:
             next_port += 1
 
 
+def _bus_devices(full_config: ConfigType, domain: str, bus_id: str) -> list[ConfigType]:
+    return [
+        device
+        for device in full_config.get(domain, [])
+        if device.get(CONF_PLATFORM) == DOMAIN
+        and str(device[CONF_I2S_AUDIO_ID]) == bus_id
+    ]
+
+
+def _validate_full_duplex(full_config: ConfigType, bus_id: str) -> None:
+    """Check that a full duplex bus has one microphone and speakers that can share its clocks and TX channel."""
+    microphones = _bus_devices(full_config, MICROPHONE_DOMAIN, bus_id)
+    speakers = _bus_devices(full_config, CONF_SPEAKER, bus_id)
+    if len(microphones) != 1 or not speakers:
+        raise cv.Invalid(
+            f"'{CONF_FULL_DUPLEX}' requires exactly one i2s_audio microphone and at least one "
+            f"i2s_audio speaker on bus '{bus_id}'"
+        )
+    microphone = microphones[0]
+    if microphone.get(CONF_PDM):
+        raise cv.Invalid(f"A PDM microphone cannot use a '{CONF_FULL_DUPLEX}' bus")
+    for speaker in speakers:
+        if speaker.get(CONF_SPDIF_MODE):
+            raise cv.Invalid(f"An SPDIF speaker cannot use a '{CONF_FULL_DUPLEX}' bus")
+        # Both directions run from the same bit and word clocks
+        for key in (
+            CONF_SAMPLE_RATE,
+            CONF_BITS_PER_SAMPLE,
+            CONF_I2S_MODE,
+            CONF_USE_APLL,
+            CONF_MCLK_MULTIPLE,
+        ):
+            if microphone[key] != speaker[key]:
+                raise cv.Invalid(
+                    f"The microphone and speaker '{speaker[CONF_ID]}' on '{CONF_FULL_DUPLEX}' bus "
+                    f"'{bus_id}' must use the same '{key}'"
+                )
+    # The TX channel is set up once from one speaker's configuration, and the speakers take turns using it
+    first = speakers[0]
+    for speaker in speakers[1:]:
+        for key in (CONF_I2S_DOUT_PIN, CONF_CHANNEL, CONF_I2S_COMM_FMT):
+            if speaker.get(key) != first.get(key):
+                raise cv.Invalid(
+                    f"The speakers on '{CONF_FULL_DUPLEX}' bus '{bus_id}' must use the same '{key}'"
+                )
+
+
 def _final_validate(_: ConfigType) -> None:
-    i2s_audio_configs = fv.full_config.get()[DOMAIN]
+    full_config = fv.full_config.get()
+    i2s_audio_configs = full_config[DOMAIN]
     variant = get_esp32_variant()
     if variant not in I2S_PORTS:
         raise cv.Invalid(f"Unsupported variant {variant}")
@@ -273,6 +341,13 @@ def _final_validate(_: ConfigType) -> None:
         )
     _assign_ports()
 
+    data = _get_data()
+    for config in i2s_audio_configs:
+        if config[CONF_FULL_DUPLEX]:
+            bus_id = str(config[CONF_ID])
+            _validate_full_duplex(full_config, bus_id)
+            data.full_duplex_buses.add(bus_id)
+
 
 FINAL_VALIDATE_SCHEMA = _final_validate
 
@@ -299,3 +374,10 @@ async def to_code(config: ConfigType) -> None:
         cg.add(var.set_bclk_pin(config[CONF_I2S_BCLK_PIN]))
     if CONF_I2S_MCLK_PIN in config:
         cg.add(var.set_mclk_pin(config[CONF_I2S_MCLK_PIN]))
+    if config[CONF_FULL_DUPLEX]:
+        cg.add_define("USE_I2S_AUDIO_FULL_DUPLEX")
+
+
+FILTER_SOURCE_FILES = filter_source_files_from_defines(
+    {"i2s_audio.cpp": "USE_I2S_AUDIO_FULL_DUPLEX"}
+)
diff --git a/esphome/components/i2s_audio/i2s_audio.cpp b/esphome/components/i2s_audio/i2s_audio.cpp
new file mode 100644
index 00000000000..d1ee8d0c73b
--- /dev/null
+++ b/esphome/components/i2s_audio/i2s_audio.cpp
@@ -0,0 +1,94 @@
+#include "i2s_audio.h"
+
+#if defined(USE_ESP32) && defined(USE_I2S_AUDIO_FULL_DUPLEX)
+
+#include "esphome/core/log.h"
+
+namespace esphome::i2s_audio {
+
+ESPHOME_LOG_TAG(TAG, "i2s_audio");
+
+void I2SAudioComponent::setup() {
+  if (!this->is_full_duplex())
+    return;
+
+  // ESP-IDF only shares the bit and word clocks between channels allocated in the same call, and deleting either
+  // channel ends the pairing. Allocate both once here and keep them for the lifetime of the device.
+  i2s_chan_config_t chan_cfg{};
+  i2s_std_config_t tx_cfg{};
+  i2s_std_config_t rx_cfg{};
+  this->audio_out_->build_full_duplex_config(chan_cfg, tx_cfg);
+  this->audio_in_->build_full_duplex_config(rx_cfg);
+
+  esp_err_t err = i2s_new_channel(&chan_cfg, &this->tx_handle_, &this->rx_handle_);
+  if (err == ESP_OK) {
+    // The first initialized channel drives the shared clocks. Use RX so the microphone runs on its own.
+    err = i2s_channel_init_std_mode(this->rx_handle_, &rx_cfg);
+  }
+  if (err == ESP_OK) {
+    err = i2s_channel_init_std_mode(this->tx_handle_, &tx_cfg);
+  }
+  if (err != ESP_OK) {
+    ESP_LOGE(TAG, "Full duplex channel setup failed: %s", esp_err_to_name(err));
+    if (this->tx_handle_ != nullptr) {
+      i2s_del_channel(this->tx_handle_);
+      this->tx_handle_ = nullptr;
+    }
+    if (this->rx_handle_ != nullptr) {
+      i2s_del_channel(this->rx_handle_);
+      this->rx_handle_ = nullptr;
+    }
+    this->mark_failed();
+  }
+}
+
+i2s_chan_handle_t I2SAudioComponent::acquire_(bool &in_use, i2s_chan_handle_t handle) {
+  if (handle == nullptr)
+    return nullptr;
+  in_use = true;
+  if (!this->update_rx_channel_()) {
+    in_use = false;
+    return nullptr;
+  }
+  return handle;
+}
+
+i2s_chan_handle_t I2SAudioComponent::acquire_rx_channel() { return this->acquire_(this->rx_in_use_, this->rx_handle_); }
+
+void I2SAudioComponent::release_rx_channel() {
+  this->rx_in_use_ = false;
+  this->update_rx_channel_();
+}
+
+i2s_chan_handle_t I2SAudioComponent::acquire_tx_channel() {
+  // Speakers sharing the bus take turns; a second one must not get the channel while the first is playing
+  if (this->tx_in_use_)
+    return nullptr;
+  return this->acquire_(this->tx_in_use_, this->tx_handle_);
+}
+
+void I2SAudioComponent::release_tx_channel() {
+  // The speaker task may have left the channel disabled already, so an invalid state error is expected here
+  i2s_channel_disable(this->tx_handle_);
+  this->tx_in_use_ = false;
+  this->update_rx_channel_();
+}
+
+bool I2SAudioComponent::update_rx_channel_() {
+  const bool needed = this->rx_in_use_ || this->tx_in_use_;
+  if (needed == this->rx_enabled_)
+    return true;
+
+  esp_err_t err = needed ? i2s_channel_enable(this->rx_handle_) : i2s_channel_disable(this->rx_handle_);
+  if (err != ESP_OK) {
+    ESP_LOGE(TAG, "Failed to %s RX channel: %s", needed ? LOG_STR_LITERAL("enable") : LOG_STR_LITERAL("disable"),
+             esp_err_to_name(err));
+    return false;
+  }
+  this->rx_enabled_ = needed;
+  return true;
+}
+
+}  // namespace esphome::i2s_audio
+
+#endif  // USE_ESP32 && USE_I2S_AUDIO_FULL_DUPLEX
diff --git a/esphome/components/i2s_audio/i2s_audio.h b/esphome/components/i2s_audio/i2s_audio.h
index 00a9705807e..b9adbe45e23 100644
--- a/esphome/components/i2s_audio/i2s_audio.h
+++ b/esphome/components/i2s_audio/i2s_audio.h
@@ -23,6 +23,15 @@ class I2SAudioBase : public Parented<I2SAudioComponent> {
   void set_mclk_multiple(i2s_mclk_multiple_t mclk_multiple) { this->mclk_multiple_ = mclk_multiple; }
 
  protected:
+  i2s_clock_src_t get_clock_source_() const {
+#ifdef I2S_CLK_SRC_APLL
+    if (this->use_apll_) {
+      return I2S_CLK_SRC_APLL;
+    }
+#endif
+    return I2S_CLK_SRC_DEFAULT;
+  }
+
   i2s_role_t i2s_role_{};
   i2s_slot_mode_t slot_mode_;
   i2s_std_slot_mask_t std_slot_mask_;
@@ -32,12 +41,51 @@ class I2SAudioBase : public Parented<I2SAudioComponent> {
   i2s_mclk_multiple_t mclk_multiple_;
 };
 
-class I2SAudioIn : public I2SAudioBase {};
+class I2SAudioIn : public I2SAudioBase {
+#ifdef USE_I2S_AUDIO_FULL_DUPLEX
+ public:
+  /// @brief Builds the RX configuration the parent uses to set up a full duplex channel pair.
+  virtual void build_full_duplex_config(i2s_std_config_t &std_cfg) = 0;
+#endif
+};
 
-class I2SAudioOut : public I2SAudioBase {};
+class I2SAudioOut : public I2SAudioBase {
+#ifdef USE_I2S_AUDIO_FULL_DUPLEX
+ public:
+  /// @brief Builds the TX configuration the parent uses to set up a full duplex channel pair. The channel
+  /// configuration (DMA layout, role, interrupt priority) is shared by both channels. Validation only puts
+  /// standard speakers on a full duplex bus, so the SPDIF speaker never gets here.
+  virtual void build_full_duplex_config(i2s_chan_config_t &chan_cfg, i2s_std_config_t &std_cfg) {}
+#endif
+};
 
 class I2SAudioComponent final : public Component {
  public:
+#ifdef USE_I2S_AUDIO_FULL_DUPLEX
+  void setup() override;
+
+  void set_audio_in(I2SAudioIn *audio_in) { this->audio_in_ = audio_in; }
+  void set_audio_out(I2SAudioOut *audio_out) { this->audio_out_ = audio_out; }
+
+  /// @brief True when a microphone and a speaker share this bus at the same time.
+  bool is_full_duplex() const { return this->audio_in_ != nullptr && this->audio_out_ != nullptr; }
+
+  /// @brief Enables the full duplex RX channel. Main loop only.
+  /// @return The enabled RX handle, or nullptr if the channel pair is unavailable
+  i2s_chan_handle_t acquire_rx_channel();
+  /// @brief Releases the RX channel; it keeps running while the TX side needs its clocks. Main loop only.
+  void release_rx_channel();
+
+  /// @brief Starts the shared clocks and hands over the full duplex TX channel, still disabled, so the caller
+  /// can register callbacks and preload data before enabling it. Main loop only.
+  /// @return The TX handle, or nullptr if the channel pair is unavailable or another speaker holds it
+  i2s_chan_handle_t acquire_tx_channel();
+  /// @brief Disables the TX channel and stops the shared clocks if the RX side is idle. Only the speaker that
+  /// acquired the channel may call this. Main loop only.
+  void release_tx_channel();
+  /// @brief True while another speaker holds the full duplex TX channel
+  bool is_tx_in_use() const { return this->tx_in_use_; }
+#endif
   i2s_std_gpio_config_t get_pin_config() const {
     return {.mclk = (gpio_num_t) this->mclk_pin_,
             .bclk = (gpio_num_t) this->bclk_pin_,
@@ -68,8 +116,20 @@ class I2SAudioComponent final : public Component {
  protected:
   Mutex lock_;
 
+#ifdef USE_I2S_AUDIO_FULL_DUPLEX
+  /// @brief Marks one side active and brings the shared clocks up; undoes the mark if that fails.
+  i2s_chan_handle_t acquire_(bool &in_use, i2s_chan_handle_t handle);
+  /// @brief Enables the RX channel while either side is active, since it drives the shared clocks.
+  bool update_rx_channel_();
+
   I2SAudioIn *audio_in_{nullptr};
   I2SAudioOut *audio_out_{nullptr};
+  i2s_chan_handle_t rx_handle_{nullptr};
+  i2s_chan_handle_t tx_handle_{nullptr};
+  bool rx_in_use_{false};
+  bool tx_in_use_{false};
+  bool rx_enabled_{false};
+#endif
   int mclk_pin_{I2S_GPIO_UNUSED};
   int bclk_pin_{I2S_GPIO_UNUSED};
   int lrclk_pin_;
diff --git a/esphome/components/i2s_audio/microphone/i2s_audio_microphone.cpp b/esphome/components/i2s_audio/microphone/i2s_audio_microphone.cpp
index 1345f0187b3..526ae304ee2 100644
--- a/esphome/components/i2s_audio/microphone/i2s_audio_microphone.cpp
+++ b/esphome/components/i2s_audio/microphone/i2s_audio_microphone.cpp
@@ -46,6 +46,13 @@ void I2SAudioMicrophone::setup() {
     return;
   }
 
+#ifdef USE_I2S_AUDIO_FULL_DUPLEX
+  if (this->parent_->is_full_duplex() && this->parent_->is_failed()) {
+    this->mark_failed(LOG_STR("Full duplex bus setup failed"));
+    return;
+  }
+#endif
+
   this->configure_stream_settings_();
 }
 
@@ -94,7 +101,44 @@ void I2SAudioMicrophone::start() {
   xSemaphoreTake(this->active_listeners_semaphore_, 0);
 }
 
+void I2SAudioMicrophone::build_std_config_(i2s_std_config_t &std_cfg) const {
+  i2s_std_slot_config_t std_slot_cfg =
+      I2S_STD_PHILIPS_SLOT_DEFAULT_CONFIG((i2s_data_bit_width_t) this->slot_bit_width_, this->slot_mode_);
+  std_slot_cfg.slot_bit_width = this->slot_bit_width_;
+  std_slot_cfg.slot_mask = this->std_slot_mask_;
+
+  i2s_std_gpio_config_t pin_config = this->parent_->get_pin_config();
+  pin_config.din = this->din_pin_;
+
+  std_cfg = {
+      .clk_cfg =
+          {
+              .sample_rate_hz = this->sample_rate_,
+              .clk_src = this->get_clock_source_(),
+              .mclk_multiple = this->mclk_multiple_,
+          },
+      .slot_cfg = std_slot_cfg,
+      .gpio_cfg = pin_config,
+  };
+}
+
+#ifdef USE_I2S_AUDIO_FULL_DUPLEX
+void I2SAudioMicrophone::build_full_duplex_config(i2s_std_config_t &std_cfg) { this->build_std_config_(std_cfg); }
+#endif
+
 bool I2SAudioMicrophone::start_driver_() {
+#ifdef USE_I2S_AUDIO_FULL_DUPLEX
+  if (this->parent_->is_full_duplex()) {
+    this->rx_handle_ = this->parent_->acquire_rx_channel();
+    if (this->rx_handle_ == nullptr) {
+      ESP_LOGE(TAG, "Full duplex channel unavailable");
+      return false;
+    }
+    this->configure_stream_settings_();
+    return true;
+  }
+#endif
+
   if (!this->parent_->try_lock()) {
     return false;  // Waiting for another i2s to return lock
   }
@@ -115,18 +159,12 @@ bool I2SAudioMicrophone::start_driver_() {
     return false;
   }
 
-  i2s_clock_src_t clk_src = I2S_CLK_SRC_DEFAULT;
-#ifdef I2S_CLK_SRC_APLL
-  if (this->use_apll_) {
-    clk_src = I2S_CLK_SRC_APLL;
-  }
-#endif
-  i2s_std_gpio_config_t pin_config = this->parent_->get_pin_config();
 #if SOC_I2S_SUPPORTS_PDM_RX
   if (this->pdm_) {
+    i2s_std_gpio_config_t pin_config = this->parent_->get_pin_config();
     i2s_pdm_rx_clk_config_t clk_cfg = {
         .sample_rate_hz = this->sample_rate_,
-        .clk_src = clk_src,
+        .clk_src = this->get_clock_source_(),
         .mclk_multiple = this->mclk_multiple_,
         .dn_sample_mode = this->pdm_dsr_,
     };
@@ -162,23 +200,8 @@ bool I2SAudioMicrophone::start_driver_() {
   } else
 #endif
   {
-    i2s_std_clk_config_t clk_cfg = {
-        .sample_rate_hz = this->sample_rate_,
-        .clk_src = clk_src,
-        .mclk_multiple = this->mclk_multiple_,
-    };
-    i2s_std_slot_config_t std_slot_cfg =
-        I2S_STD_PHILIPS_SLOT_DEFAULT_CONFIG((i2s_data_bit_width_t) this->slot_bit_width_, this->slot_mode_);
-    std_slot_cfg.slot_bit_width = this->slot_bit_width_;
-    std_slot_cfg.slot_mask = this->std_slot_mask_;
-
-    pin_config.din = this->din_pin_;
-
-    i2s_std_config_t std_cfg = {
-        .clk_cfg = clk_cfg,
-        .slot_cfg = std_slot_cfg,
-        .gpio_cfg = pin_config,
-    };
+    i2s_std_config_t std_cfg;
+    this->build_std_config_(std_cfg);
     /* Initialize the channel */
     err = i2s_channel_init_std_mode(this->rx_handle_, &std_cfg);
   }
@@ -210,6 +233,17 @@ void I2SAudioMicrophone::stop_driver_() {
   // There is no harm continuing to unload the driver if an error is ever returned by the various functions. This
   // ensures that we stop/unload the driver when it only partially starts.
 
+#ifdef USE_I2S_AUDIO_FULL_DUPLEX
+  if (this->parent_->is_full_duplex()) {
+    // The parent owns the channel pair, so only hand the RX channel back
+    if (this->rx_handle_ != nullptr) {
+      this->parent_->release_rx_channel();
+      this->rx_handle_ = nullptr;
+    }
+    return;
+  }
+#endif
+
   esp_err_t err;
   if (this->rx_handle_ != nullptr) {
     /* Have to stop the channel before deleting it */
diff --git a/esphome/components/i2s_audio/microphone/i2s_audio_microphone.h b/esphome/components/i2s_audio/microphone/i2s_audio_microphone.h
index 1b17380ed87..c5ed52f6514 100644
--- a/esphome/components/i2s_audio/microphone/i2s_audio_microphone.h
+++ b/esphome/components/i2s_audio/microphone/i2s_audio_microphone.h
@@ -33,7 +33,14 @@ class I2SAudioMicrophone final : public I2SAudioIn, public microphone::Microphon
   void set_pdm_dsr(i2s_pdm_dsr_t pdm_dsr) { this->pdm_dsr_ = pdm_dsr; }
 #endif
 
+#ifdef USE_I2S_AUDIO_FULL_DUPLEX
+  void build_full_duplex_config(i2s_std_config_t &std_cfg) override;
+#endif
+
  protected:
+  /// @brief Builds the standard (non-PDM) mode configuration from the configured settings.
+  void build_std_config_(i2s_std_config_t &std_cfg) const;
+
   /// @brief Starts the I2S driver. Updates the ``audio_stream_info_`` member variable with the current setttings.
   /// @return True if succesful, false otherwise
   bool start_driver_();
@@ -59,7 +66,7 @@ class I2SAudioMicrophone final : public I2SAudioIn, public microphone::Microphon
   TaskHandle_t task_handle_{nullptr};
 
   gpio_num_t din_pin_{I2S_GPIO_UNUSED};
-  i2s_chan_handle_t rx_handle_;
+  i2s_chan_handle_t rx_handle_{nullptr};
 #if SOC_I2S_SUPPORTS_PDM_RX
   i2s_pdm_dsr_t pdm_dsr_{I2S_PDM_DSR_8S};
 #endif
diff --git a/esphome/components/i2s_audio/speaker/__init__.py b/esphome/components/i2s_audio/speaker/__init__.py
index e4ea186199d..ddbe08922fe 100644
--- a/esphome/components/i2s_audio/speaker/__init__.py
+++ b/esphome/components/i2s_audio/speaker/__init__.py
@@ -20,6 +20,7 @@ from esphome.types import ConfigType
 
 from .. import (
     CONF_I2S_AUDIO_ID,
+    CONF_I2S_COMM_FMT,
     CONF_I2S_DOUT_PIN,
     CONF_I2S_MODE,
     CONF_LEFT,
@@ -27,6 +28,7 @@ from .. import (
     CONF_MONO,
     CONF_PRIMARY,
     CONF_RIGHT,
+    CONF_SPDIF_MODE,
     CONF_STEREO,
     CONF_USE_APLL,
     I2SAudioOut,
@@ -46,9 +48,7 @@ I2SAudioSpeakerBase = i2s_audio_ns.class_(
 I2SAudioSpeaker = i2s_audio_ns.class_("I2SAudioSpeaker", I2SAudioSpeakerBase)
 
 CONF_DAC_TYPE = "dac_type"
-CONF_I2S_COMM_FMT = "i2s_comm_fmt"
 CONF_KEEP_ALIVE = "keep_alive"
-CONF_SPDIF_MODE = "spdif_mode"
 
 I2SAudioSpeakerBase = i2s_audio_ns.class_(
     "I2SAudioSpeakerBase", cg.Component, speaker.Speaker, I2SAudioOut
diff --git a/esphome/components/i2s_audio/speaker/i2s_audio_spdif.cpp b/esphome/components/i2s_audio/speaker/i2s_audio_spdif.cpp
index 3938d777717..46d6473983d 100644
--- a/esphome/components/i2s_audio/speaker/i2s_audio_spdif.cpp
+++ b/esphome/components/i2s_audio/speaker/i2s_audio_spdif.cpp
@@ -467,14 +467,6 @@ esp_err_t I2SAudioSpeakerSPDIF::start_i2s_driver(audio::AudioStreamInfo &audio_s
     return ESP_ERR_INVALID_STATE;
   }
 
-  i2s_clock_src_t clk_src = I2S_CLK_SRC_DEFAULT;
-
-#if SOC_CLK_APLL_SUPPORTED
-  if (this->use_apll_) {
-    clk_src = i2s_clock_src_t::I2S_CLK_SRC_APLL;
-  }
-#endif  // SOC_CLK_APLL_SUPPORTED
-
   // SPDIF mode: fixed configuration for BMC encoding
   // For new driver, dma_frame_num is in I2S frames (8 bytes each for 32-bit stereo)
   uint32_t dma_buffer_length = SPDIF_BLOCK_I2S_FRAMES;  // One SPDIF block = 384 I2S frames = 3072 bytes
@@ -496,7 +488,7 @@ esp_err_t I2SAudioSpeakerSPDIF::start_i2s_driver(audio::AudioStreamInfo &audio_s
   // SPDIF: double sample rate for BMC, 32-bit stereo, only data pin needed
   i2s_std_clk_config_t clk_cfg = {
       .sample_rate_hz = this->sample_rate_ * 2,
-      .clk_src = clk_src,
+      .clk_src = this->get_clock_source_(),
       .mclk_multiple = this->mclk_multiple_,
   };
 
diff --git a/esphome/components/i2s_audio/speaker/i2s_audio_speaker.cpp b/esphome/components/i2s_audio/speaker/i2s_audio_speaker.cpp
index 85c0e6358a2..f14626dd47f 100644
--- a/esphome/components/i2s_audio/speaker/i2s_audio_speaker.cpp
+++ b/esphome/components/i2s_audio/speaker/i2s_audio_speaker.cpp
@@ -41,6 +41,17 @@ void I2SAudioSpeakerBase::setup() {
   this->set_volume(this->volume_);
   this->set_mute_state(this->mute_state_);
 
+#ifdef USE_I2S_AUDIO_FULL_DUPLEX
+  // The parent set up before us and already routed dout to the shared TX channel, which is never re-initialized.
+  // Parking would detach the pin for good. SPDIF speakers cannot use a full duplex bus.
+  if (this->parent_->is_full_duplex()) {
+    if (this->parent_->is_failed()) {
+      this->mark_failed(LOG_STR("Full duplex bus setup failed"));
+    }
+    return;
+  }
+#endif
+
   // Until the I2S driver first starts, dout sits in its reset state (often pulled high, or a JTAG
   // function on the ESP32-S3), which keeps a SPDIF optical transmitter lit. Park it low now.
   this->park_dout_pin_();
@@ -130,7 +141,7 @@ void I2SAudioSpeakerBase::loop() {
 
   // Handle the speaker's state
   switch (this->state_) {
-    case speaker::STATE_STARTING:
+    case speaker::STATE_STARTING: {
       if (this->status_has_error()) {
         break;
       }
@@ -140,7 +151,21 @@ void I2SAudioSpeakerBase::loop() {
         break;
       }
 
-      if (this->start_i2s_driver(this->audio_stream_info_) != ESP_OK) {
+#ifdef USE_I2S_AUDIO_FULL_DUPLEX
+      if (this->parent_->is_tx_in_use()) {
+        // Another speaker on the bus is playing; wait for it to release the channel
+        break;
+      }
+#endif
+      const esp_err_t err = this->start_i2s_driver(this->audio_stream_info_);
+      if (err == ESP_ERR_NOT_SUPPORTED) {
+        // Retrying cannot help; stay stopped so the audio source gives up instead of waiting forever
+        ESP_LOGE(TAG, "Stream format not supported; not starting");
+        this->rejected_stream_info_ = this->audio_stream_info_;
+        this->state_ = speaker::STATE_STOPPED;
+        break;
+      }
+      if (err != ESP_OK) {
         ESP_LOGE(TAG, "Driver failed to start; retrying in 1 second");
         this->status_momentary_error(1000);
         break;
@@ -159,6 +184,7 @@ void I2SAudioSpeakerBase::loop() {
         this->stop_i2s_driver_(false);  // Stops the driver to return the lock; will be reloaded in next attempt
       }
       break;
+    }
     case speaker::STATE_RUNNING:   // Intentional fallthrough
     case speaker::STATE_STOPPING:  // Intentional fallthrough
     case speaker::STATE_STOPPED:
@@ -240,6 +266,9 @@ void I2SAudioSpeakerBase::start() {
     return;
   if ((this->state_ == speaker::STATE_STARTING) || (this->state_ == speaker::STATE_RUNNING))
     return;
+  // play() calls start() on every write, so without this a rejected stream would be retried and logged nonstop
+  if (this->rejected_stream_info_.has_value() && this->rejected_stream_info_.value() == this->audio_stream_info_)
+    return;
 
   xEventGroupSetBits(this->event_group_, SpeakerEventGroupBits::COMMAND_START);
 }
@@ -277,6 +306,15 @@ esp_err_t I2SAudioSpeakerBase::init_i2s_channel_(const i2s_chan_config_t &chan_c
     return err;
   }
 
+  err = this->prepare_event_queues_(event_queue_size);
+  if (err != ESP_OK) {
+    this->delete_channel_();
+    this->parent_->unlock();
+  }
+  return err;
+}
+
+esp_err_t I2SAudioSpeakerBase::prepare_event_queues_(size_t event_queue_size) {
   // Both queues are drained by the speaker task before it preloads, whether the channel is new or kept
   if (this->i2s_event_queue_ == nullptr) {
     this->i2s_event_queue_ = xQueueCreate(event_queue_size, sizeof(int64_t));
@@ -290,15 +328,41 @@ esp_err_t I2SAudioSpeakerBase::init_i2s_channel_(const i2s_chan_config_t &chan_c
 
   if (this->i2s_event_queue_ == nullptr || this->write_records_queue_ == nullptr) {
     ESP_LOGE(TAG, "Failed to allocate I2S event queue(s)");
-    this->delete_channel_();
-    this->parent_->unlock();
     return ESP_ERR_NO_MEM;
   }
 
   return ESP_OK;
 }
 
+#ifdef USE_I2S_AUDIO_FULL_DUPLEX
+esp_err_t I2SAudioSpeakerBase::acquire_full_duplex_channel_(size_t event_queue_size) {
+  this->tx_handle_ = this->parent_->acquire_tx_channel();
+  if (this->tx_handle_ == nullptr) {
+    ESP_LOGE(TAG, "Full duplex channel unavailable");
+    return ESP_ERR_INVALID_STATE;
+  }
+
+  esp_err_t err = this->prepare_event_queues_(event_queue_size);
+  if (err != ESP_OK) {
+    this->parent_->release_tx_channel();
+    this->tx_handle_ = nullptr;
+  }
+  return err;
+}
+#endif
+
 void I2SAudioSpeakerBase::stop_i2s_driver_(bool keep_channel) {
+#ifdef USE_I2S_AUDIO_FULL_DUPLEX
+  if (this->parent_->is_full_duplex()) {
+    // The parent owns the channel pair and its pins, so only hand the TX channel back
+    if (this->tx_handle_ != nullptr) {
+      this->parent_->release_tx_channel();
+      this->tx_handle_ = nullptr;
+    }
+    return;
+  }
+#endif
+
   if (this->tx_handle_ != nullptr) {
     i2s_channel_disable(this->tx_handle_);
     // A kept channel lets the next start skip i2s_new_channel and i2s_channel_init_std_mode, whose GPIO and
@@ -372,9 +436,9 @@ void I2SAudioSpeakerBase::apply_software_volume_(uint8_t *data, size_t bytes_rea
                            this->current_stream_info_.bytes_to_samples(bytes_read));
 }
 
-bool I2SAudioSpeakerBase::esp32_mono_swap_needed_() const {
+bool I2SAudioSpeakerBase::esp32_mono_swap_needed(const audio::AudioStreamInfo &stream_info) {
 #ifdef USE_ESP32_VARIANT_ESP32
-  return this->output_stream_info_.get_channels() == 1 && this->output_stream_info_.get_bits_per_sample() == 16;
+  return stream_info.get_channels() == 1 && stream_info.get_bits_per_sample() == 16;
 #else
   return false;
 #endif  // USE_ESP32_VARIANT_ESP32
diff --git a/esphome/components/i2s_audio/speaker/i2s_audio_speaker.h b/esphome/components/i2s_audio/speaker/i2s_audio_speaker.h
index 07b7e5d1905..03213347f0e 100644
--- a/esphome/components/i2s_audio/speaker/i2s_audio_speaker.h
+++ b/esphome/components/i2s_audio/speaker/i2s_audio_speaker.h
@@ -127,6 +127,18 @@ class I2SAudioSpeakerBase : public I2SAudioOut, public speaker::Speaker, public
   esp_err_t init_i2s_channel_(const i2s_chan_config_t &chan_cfg, const i2s_std_config_t &std_cfg,
                               size_t event_queue_size);
 
+  /// @brief Creates the lockstep queues unless they exist already.
+  /// @param event_queue_size Size of each queue
+  /// @return ESP_OK if successful, or ESP_ERR_NO_MEM
+  esp_err_t prepare_event_queues_(size_t event_queue_size);
+
+#ifdef USE_I2S_AUDIO_FULL_DUPLEX
+  /// @brief Takes the TX channel of the parent's full duplex pair and prepares the event queues.
+  /// @param event_queue_size Size of the event queue
+  /// @return ESP_OK if successful, or an error code. On failure, hands the channel back to the parent.
+  esp_err_t acquire_full_duplex_channel_(size_t event_queue_size);
+#endif
+
   /// @brief Stops the I2S driver and unlocks the I2S port; keep_channel leaves the disabled channel allocated
   void stop_i2s_driver_(bool keep_channel);
 
@@ -160,8 +172,10 @@ class I2SAudioSpeakerBase : public I2SAudioOut, public speaker::Speaker, public
   /// @param bytes_read Number of bytes of audio data
   void apply_software_volume_(uint8_t *data, size_t bytes_read);
 
+  /// @brief Whether 16-bit mono samples in this format need the ESP32 (non-variant) pair swap.
+  static bool esp32_mono_swap_needed(const audio::AudioStreamInfo &stream_info);
   /// @brief Whether the output is 16-bit mono on the original ESP32, which sends each pair of samples swapped.
-  bool esp32_mono_swap_needed_() const;
+  bool esp32_mono_swap_needed_() const { return esp32_mono_swap_needed(this->output_stream_info_); }
 
   /// @brief Swap adjacent 16-bit mono samples for ESP32 (non-variant) hardware quirk.
   /// Only applies when esp32_mono_swap_needed_() is true. `data` must start on a DMA word and hold whole pairs.
@@ -182,6 +196,9 @@ class I2SAudioSpeakerBase : public I2SAudioOut, public speaker::Speaker, public
 
   optional<uint32_t> timeout_;
 
+  // A format start_i2s_driver() refused. Those checks compare against fixed settings, so it can never start.
+  optional<audio::AudioStreamInfo> rejected_stream_info_;
+
   bool pause_state_{false};
   bool keep_alive_{false};
 
diff --git a/esphome/components/i2s_audio/speaker/i2s_audio_speaker_standard.cpp b/esphome/components/i2s_audio/speaker/i2s_audio_speaker_standard.cpp
index 16abb2f22ef..73ad924fad7 100644
--- a/esphome/components/i2s_audio/speaker/i2s_audio_speaker_standard.cpp
+++ b/esphome/components/i2s_audio/speaker/i2s_audio_speaker_standard.cpp
@@ -86,7 +86,7 @@ void I2SAudioSpeaker::run_speaker_task() {
   // The ring buffer holds input-format audio (what play() receives), so size it from the input stream info.
   const size_t bytes_per_frame = this->current_stream_info_.frames_to_bytes(1);
   // Hand over whole ESP32 mono sample pairs so writes stay word-aligned
-  const size_t source_alignment = bytes_per_frame * this->dma_frame_multiple_();
+  const size_t source_alignment = bytes_per_frame * dma_frame_multiple(this->output_stream_info_);
   const bool pair_aligned = source_alignment > bytes_per_frame;
   // Round the ring buffer size down to a multiple of source_alignment so the wrap boundary avoids splices.
   const size_t ring_buffer_size =
@@ -111,7 +111,7 @@ void I2SAudioSpeaker::run_speaker_task() {
   } else {
     // Should not happen for a READY channel; fall back to the requested size.
     dma_buffer_bytes = this->output_stream_info_.frames_to_bytes(
-        dma_buffer_frames(this->output_stream_info_, this->dma_frame_multiple_()));
+        dma_buffer_frames(this->output_stream_info_, dma_frame_multiple(this->output_stream_info_)));
   }
   // dma_buffer_bytes counts output-format bytes; convert with the output stream info.
   const uint32_t frames_per_dma_buffer = this->output_stream_info_.bytes_to_frames(dma_buffer_bytes);
@@ -442,6 +442,25 @@ esp_err_t I2SAudioSpeaker::start_i2s_driver(audio::AudioStreamInfo &audio_stream
   }
 #endif  // USE_ESP32_VARIANT_ESP32
 
+#ifdef USE_I2S_AUDIO_FULL_DUPLEX
+  if (this->parent_->is_full_duplex()) {
+    // The parent set up the channel once from the configured format, so the stream must produce exactly that
+    const audio::AudioStreamInfo required = this->full_duplex_stream_info_();
+    if (this->output_stream_info_ != required) {
+      ESP_LOGE(TAG, "Full duplex requires %u-bit, %u channel audio at %" PRIu32 " Hz",
+               (unsigned) required.get_bits_per_sample(), (unsigned) required.get_channels(),
+               required.get_sample_rate());
+      if (this->output_stream_info_.get_channels() != required.get_channels()) {
+        ESP_LOGE(TAG, "A resampler does not change the channel count; add a mixer speaker with num_channels: %u",
+                 (unsigned) required.get_channels());
+      }
+      return ESP_ERR_NOT_SUPPORTED;
+    }
+    // The speaker task will enable the channel after preloading.
+    return this->acquire_full_duplex_channel_(I2S_EVENT_QUEUE_COUNT);
+  }
+#endif  // USE_I2S_AUDIO_FULL_DUPLEX
+
   if (!this->parent_->try_lock()) {
     ESP_LOGE(TAG, "Parent bus is busy");
     return ESP_ERR_INVALID_STATE;
@@ -457,25 +476,37 @@ esp_err_t I2SAudioSpeaker::start_i2s_driver(audio::AudioStreamInfo &audio_stream
 
   this->current_stream_info_ = audio_stream_info;
 
+  i2s_chan_config_t chan_cfg;
+  i2s_std_config_t std_cfg;
+  this->build_i2s_config_(this->output_stream_info_, chan_cfg, std_cfg);
+
+  // The speaker task will enable the channel after preloading.
+  return this->init_i2s_channel_(chan_cfg, std_cfg, I2S_EVENT_QUEUE_COUNT);
+}
+
+#ifdef USE_I2S_AUDIO_FULL_DUPLEX
+audio::AudioStreamInfo I2SAudioSpeaker::full_duplex_stream_info_() const {
+  return audio::AudioStreamInfo(static_cast<uint8_t>(this->slot_bit_width_),
+                                this->slot_mode_ == I2S_SLOT_MODE_STEREO ? 2 : 1, this->sample_rate_);
+}
+
+void I2SAudioSpeaker::build_full_duplex_config(i2s_chan_config_t &chan_cfg, i2s_std_config_t &std_cfg) {
+  this->build_i2s_config_(this->full_duplex_stream_info_(), chan_cfg, std_cfg);
+}
+#endif  // USE_I2S_AUDIO_FULL_DUPLEX
+
+void I2SAudioSpeaker::build_i2s_config_(const audio::AudioStreamInfo &output_stream_info, i2s_chan_config_t &chan_cfg,
+                                        i2s_std_config_t &std_cfg) const {
   // The DMA buffers hold output-format (post-narrowing) samples, so size them from the output stream info.
-  uint32_t dma_buffer_length = dma_buffer_frames(this->output_stream_info_, this->dma_frame_multiple_());
-
-  i2s_role_t i2s_role = this->i2s_role_;
-  i2s_clock_src_t clk_src = I2S_CLK_SRC_DEFAULT;
-
-#if SOC_CLK_APLL_SUPPORTED
-  if (this->use_apll_) {
-    clk_src = i2s_clock_src_t::I2S_CLK_SRC_APLL;
-  }
-#endif  // SOC_CLK_APLL_SUPPORTED
+  uint32_t dma_buffer_length = dma_buffer_frames(output_stream_info, dma_frame_multiple(output_stream_info));
 
   // Log DMA configuration for debugging
   ESP_LOGV(TAG, "I2S DMA config: %zu buffers x %lu frames", (size_t) DMA_BUFFERS_COUNT,
            (unsigned long) dma_buffer_length);
 
-  i2s_chan_config_t chan_cfg = {
+  chan_cfg = {
       .id = this->parent_->get_port(),
-      .role = i2s_role,
+      .role = this->i2s_role_,
       .dma_desc_num = DMA_BUFFERS_COUNT,
       .dma_frame_num = dma_buffer_length,
       .auto_clear = true,
@@ -484,22 +515,22 @@ esp_err_t I2SAudioSpeaker::start_i2s_driver(audio::AudioStreamInfo &audio_stream
 
   // Build standard I2S clock/slot/gpio configuration
   i2s_std_clk_config_t clk_cfg = {
-      .sample_rate_hz = audio_stream_info.get_sample_rate(),
-      .clk_src = clk_src,
+      .sample_rate_hz = output_stream_info.get_sample_rate(),
+      .clk_src = this->get_clock_source_(),
       .mclk_multiple = this->mclk_multiple_,
   };
 
   i2s_slot_mode_t slot_mode = this->slot_mode_;
   i2s_std_slot_mask_t slot_mask = this->std_slot_mask_;
-  if (audio_stream_info.get_channels() == 1) {
+  if (output_stream_info.get_channels() == 1) {
     slot_mode = I2S_SLOT_MODE_MONO;
-  } else if (audio_stream_info.get_channels() == 2) {
+  } else if (output_stream_info.get_channels() == 2) {
     slot_mode = I2S_SLOT_MODE_STEREO;
     slot_mask = I2S_STD_SLOT_BOTH;
   }
 
   // Configure the data bit width from the output (post-narrowing) format, which is what is clocked out.
-  const i2s_data_bit_width_t data_bit_width = (i2s_data_bit_width_t) this->output_stream_info_.get_bits_per_sample();
+  const i2s_data_bit_width_t data_bit_width = (i2s_data_bit_width_t) output_stream_info.get_bits_per_sample();
   i2s_std_slot_config_t slot_cfg;
   switch (this->i2s_comm_fmt_) {
     case I2SCommFmt::PCM:
@@ -535,20 +566,11 @@ esp_err_t I2SAudioSpeaker::start_i2s_driver(audio::AudioStreamInfo &audio_stream
   i2s_std_gpio_config_t gpio_cfg = this->parent_->get_pin_config();
   gpio_cfg.dout = this->dout_pin_;
 
-  i2s_std_config_t std_cfg = {
+  std_cfg = {
       .clk_cfg = clk_cfg,
       .slot_cfg = slot_cfg,
       .gpio_cfg = gpio_cfg,
   };
-
-  esp_err_t err = this->init_i2s_channel_(chan_cfg, std_cfg, I2S_EVENT_QUEUE_COUNT);
-  if (err != ESP_OK) {
-    return err;
-  }
-
-  // The speaker task will enable the channel after preloading.
-
-  return ESP_OK;
 }
 
 }  // namespace esphome::i2s_audio
diff --git a/esphome/components/i2s_audio/speaker/i2s_audio_speaker_standard.h b/esphome/components/i2s_audio/speaker/i2s_audio_speaker_standard.h
index 01390dfdf70..fb1184bb71e 100644
--- a/esphome/components/i2s_audio/speaker/i2s_audio_speaker_standard.h
+++ b/esphome/components/i2s_audio/speaker/i2s_audio_speaker_standard.h
@@ -20,12 +20,28 @@ class I2SAudioSpeaker final : public I2SAudioSpeakerBase {
 
   void set_i2s_comm_fmt(I2SCommFmt fmt) { this->i2s_comm_fmt_ = fmt; }
 
+#ifdef USE_I2S_AUDIO_FULL_DUPLEX
+  void build_full_duplex_config(i2s_chan_config_t &chan_cfg, i2s_std_config_t &std_cfg) override;
+#endif
+
  protected:
   void run_speaker_task() override;
   esp_err_t start_i2s_driver(audio::AudioStreamInfo &audio_stream_info) override;
 
+  /// @brief Builds the channel and standard mode configuration for the given output format.
+  /// @param output_stream_info Format clocked out of the I2S peripheral
+  void build_i2s_config_(const audio::AudioStreamInfo &output_stream_info, i2s_chan_config_t &chan_cfg,
+                         i2s_std_config_t &std_cfg) const;
+
+#ifdef USE_I2S_AUDIO_FULL_DUPLEX
+  /// @brief The output format of a full duplex bus, fixed by the configuration since the channel is set up once.
+  audio::AudioStreamInfo full_duplex_stream_info_() const;
+#endif
+
   /// @brief Frame multiple for DMA buffers and writes; 2 keeps ESP32 mono sample pairs word-aligned.
-  uint32_t dma_frame_multiple_() const { return this->esp32_mono_swap_needed_() ? 2 : 1; }
+  static uint32_t dma_frame_multiple(const audio::AudioStreamInfo &stream_info) {
+    return esp32_mono_swap_needed(stream_info) ? 2 : 1;
+  }
 
   I2SCommFmt i2s_comm_fmt_{I2SCommFmt::STANDARD};
 };
diff --git a/esphome/core/defines.h b/esphome/core/defines.h
index c901ff3e844..0655c4a399c 100644
--- a/esphome/core/defines.h
+++ b/esphome/core/defines.h
@@ -95,6 +95,7 @@
 #define USE_HOMEASSISTANT_TIME
 #define USE_HOMEASSISTANT_TIMEZONE
 #define USE_HTTP_REQUEST_OTA_WATCHDOG_TIMEOUT 8000  // NOLINT
+#define USE_I2S_AUDIO_FULL_DUPLEX
 #define USE_I2S_AUDIO_SPDIF_MODE
 #define USE_IMAGE
 #define USE_IMPROV_BLE_STATE_CALLBACK
diff --git a/tests/component_tests/i2s_audio/test_full_duplex_multiple_speakers.yaml b/tests/component_tests/i2s_audio/test_full_duplex_multiple_speakers.yaml
new file mode 100644
index 00000000000..5cc4fb38125
--- /dev/null
+++ b/tests/component_tests/i2s_audio/test_full_duplex_multiple_speakers.yaml
@@ -0,0 +1,42 @@
+esphome:
+  name: test
+
+esp32:
+  board: esp32dev
+  framework:
+    type: esp-idf
+
+i2s_audio:
+  - id: duplex_bus
+    i2s_bclk_pin: GPIO5
+    i2s_lrclk_pin: GPIO4
+    full_duplex: true
+
+microphone:
+  - platform: i2s_audio
+    id: duplex_mic
+    i2s_audio_id: duplex_bus
+    i2s_din_pin: GPIO16
+    adc_type: external
+    sample_rate: 48000
+    bits_per_sample: 32bit
+
+speaker:
+  - platform: i2s_audio
+    id: duplex_speaker_a
+    i2s_audio_id: duplex_bus
+    i2s_dout_pin:
+      number: GPIO17
+      allow_other_uses: true
+    dac_type: external
+    sample_rate: 48000
+    bits_per_sample: 32bit
+  - platform: i2s_audio
+    id: duplex_speaker_b
+    i2s_audio_id: duplex_bus
+    i2s_dout_pin:
+      number: GPIO17
+      allow_other_uses: true
+    dac_type: external
+    sample_rate: 48000
+    bits_per_sample: 32bit
diff --git a/tests/component_tests/i2s_audio/test_i2s_audio.py b/tests/component_tests/i2s_audio/test_i2s_audio.py
new file mode 100644
index 00000000000..f92d0ca9414
--- /dev/null
+++ b/tests/component_tests/i2s_audio/test_i2s_audio.py
@@ -0,0 +1,141 @@
+"""Tests for the i2s_audio full duplex bus."""
+
+from __future__ import annotations
+
+from collections.abc import Callable
+from pathlib import Path
+from typing import Any
+
+import pytest
+
+from esphome import config_validation as cv
+from esphome.components.i2s_audio import _validate_full_duplex
+from esphome.core import CORE, ID
+
+BUS_ID = "duplex_bus"
+
+
+def _device(**overrides: Any) -> dict[str, Any]:
+    return {
+        "platform": "i2s_audio",
+        "id": ID("device", is_declaration=True),
+        "i2s_audio_id": ID(BUS_ID, is_declaration=False),
+        "i2s_dout_pin": 17,
+        "channel": "stereo",
+        "i2s_comm_fmt": "stand_i2s",
+        "sample_rate": 48000,
+        "bits_per_sample": 32,
+        "i2s_mode": "primary",
+        "use_apll": False,
+        "mclk_multiple": 256,
+    } | overrides
+
+
+def _full_config(
+    microphones: list[dict[str, Any]], speakers: list[dict[str, Any]]
+) -> dict[str, Any]:
+    return {"microphone": microphones, "speaker": speakers}
+
+
+def test_full_duplex_generates_code(
+    generate_main: Callable[[str | Path], str],
+) -> None:
+    """The microphone and every speaker are registered with the bus and the full duplex code is enabled."""
+    main_cpp = generate_main(
+        "tests/component_tests/i2s_audio/test_full_duplex_multiple_speakers.yaml"
+    )
+
+    assert "duplex_bus->set_audio_in(duplex_mic);" in main_cpp
+    assert "duplex_bus->set_audio_out(duplex_speaker_a);" in main_cpp
+    assert "duplex_bus->set_audio_out(duplex_speaker_b);" in main_cpp
+    assert "USE_I2S_AUDIO_FULL_DUPLEX" in {define.name for define in CORE.defines}
+
+
+_OTHER_BUS = _device(i2s_audio_id=ID("other_bus", is_declaration=False))
+
+
+@pytest.mark.parametrize(
+    ("microphones", "speakers"),
+    [
+        pytest.param([_device(pdm=False)], [_device(spdif_mode=False)], id="matching"),
+        pytest.param(
+            [_device(), _OTHER_BUS], [_device(), _OTHER_BUS], id="other-bus-ignored"
+        ),
+        pytest.param(
+            [_device()], [_device(), _device(), _device()], id="several-speakers"
+        ),
+    ],
+)
+def test_full_duplex_accepts(
+    microphones: list[dict[str, Any]], speakers: list[dict[str, Any]]
+) -> None:
+    """Devices with the same clock and TX settings share the bus; other buses do not count."""
+    _validate_full_duplex(_full_config(microphones, speakers), BUS_ID)
+
+
+@pytest.mark.parametrize(
+    ("microphones", "speakers"),
+    [
+        ([], [_device()]),
+        ([_device()], []),
+        ([_device(), _device()], [_device()]),
+    ],
+)
+def test_full_duplex_requires_one_microphone_and_a_speaker(
+    microphones: list[dict[str, Any]], speakers: list[dict[str, Any]]
+) -> None:
+    """Exactly one microphone and at least one speaker must use the bus."""
+    with pytest.raises(cv.Invalid, match="exactly one i2s_audio microphone"):
+        _validate_full_duplex(_full_config(microphones, speakers), BUS_ID)
+
+
+@pytest.mark.parametrize(
+    ("microphone", "speaker", "error_match"),
+    [
+        pytest.param(_device(pdm=True), _device(), "PDM microphone", id="pdm"),
+        pytest.param(_device(), _device(spdif_mode=True), "SPDIF speaker", id="spdif"),
+    ],
+)
+def test_full_duplex_rejects_unsupported_devices(
+    microphone: dict[str, Any], speaker: dict[str, Any], error_match: str
+) -> None:
+    """PDM receive and SPDIF output cannot share the standard mode clocks."""
+    with pytest.raises(cv.Invalid, match=error_match):
+        _validate_full_duplex(_full_config([microphone], [speaker]), BUS_ID)
+
+
+@pytest.mark.parametrize(
+    ("key", "value"),
+    [
+        ("sample_rate", 16000),
+        ("bits_per_sample", 16),
+        ("i2s_mode", "secondary"),
+        ("use_apll", True),
+        ("mclk_multiple", 384),
+    ],
+)
+def test_full_duplex_rejects_mismatched_clock_settings(key: str, value: Any) -> None:
+    """Settings that shape the shared clocks must match."""
+    with pytest.raises(cv.Invalid, match=f"must use the same '{key}'"):
+        _validate_full_duplex(
+            _full_config([_device()], [_device(**{key: value})]), BUS_ID
+        )
+
+
+@pytest.mark.parametrize(
+    ("key", "value"),
+    [
+        ("i2s_dout_pin", 18),
+        ("channel", "mono"),
+        ("i2s_comm_fmt", "stand_msb"),
+    ],
+)
+def test_full_duplex_rejects_mismatched_speakers(key: str, value: Any) -> None:
+    """Settings that shape the TX channel must match across speakers."""
+    with pytest.raises(
+        cv.Invalid,
+        match=f"speakers on 'full_duplex' bus '{BUS_ID}' must use the same '{key}'",
+    ):
+        _validate_full_duplex(
+            _full_config([_device()], [_device(), _device(**{key: value})]), BUS_ID
+        )
diff --git a/tests/components/i2s_audio/common-full_duplex.yaml b/tests/components/i2s_audio/common-full_duplex.yaml
new file mode 100644
index 00000000000..06ec6a87c96
--- /dev/null
+++ b/tests/components/i2s_audio/common-full_duplex.yaml
@@ -0,0 +1,26 @@
+i2s_audio:
+  - id: i2s_duplex_bus
+    i2s_bclk_pin: ${i2s_bclk_pin}
+    i2s_lrclk_pin: ${i2s_lrclk_pin}
+    i2s_mclk_pin: ${i2s_mclk_pin}
+    full_duplex: true
+
+microphone:
+  - platform: i2s_audio
+    id: duplex_mic
+    i2s_audio_id: i2s_duplex_bus
+    i2s_din_pin: ${i2s_din_pin}
+    adc_type: external
+    sample_rate: 48000
+    bits_per_sample: 32bit
+    channel: stereo
+
+speaker:
+  - platform: i2s_audio
+    id: duplex_speaker
+    i2s_audio_id: i2s_duplex_bus
+    i2s_dout_pin: ${i2s_dout_pin}
+    dac_type: external
+    sample_rate: 48000
+    bits_per_sample: 32bit
+    channel: stereo
diff --git a/tests/components/i2s_audio/test-full_duplex.esp32-idf.yaml b/tests/components/i2s_audio/test-full_duplex.esp32-idf.yaml
new file mode 100644
index 00000000000..4e8c9b4e4c8
--- /dev/null
+++ b/tests/components/i2s_audio/test-full_duplex.esp32-idf.yaml
@@ -0,0 +1,9 @@
+substitutions:
+  i2s_bclk_pin: GPIO5
+  i2s_lrclk_pin: GPIO4
+  i2s_mclk_pin: GPIO15
+  i2s_din_pin: GPIO16
+  i2s_dout_pin: GPIO17
+
+packages:
+  i2s_audio: !include common-full_duplex.yaml
diff --git a/tests/components/i2s_audio/test-full_duplex.esp32-s3-idf.yaml b/tests/components/i2s_audio/test-full_duplex.esp32-s3-idf.yaml
new file mode 100644
index 00000000000..4e8c9b4e4c8
--- /dev/null
+++ b/tests/components/i2s_audio/test-full_duplex.esp32-s3-idf.yaml
@@ -0,0 +1,9 @@
+substitutions:
+  i2s_bclk_pin: GPIO5
+  i2s_lrclk_pin: GPIO4
+  i2s_mclk_pin: GPIO15
+  i2s_din_pin: GPIO16
+  i2s_dout_pin: GPIO17
+
+packages:
+  i2s_audio: !include common-full_duplex.yaml