diff --git a/esphome/components/mqtt/custom_mqtt_device.cpp b/esphome/components/mqtt/custom_mqtt_device.cpp
index 7ff65bb42cd..64521f5cf3c 100644
--- a/esphome/components/mqtt/custom_mqtt_device.cpp
+++ b/esphome/components/mqtt/custom_mqtt_device.cpp
@@ -18,7 +18,7 @@ bool CustomMQTTDevice::publish(const std::string &topic, float value, int8_t num
 }
 bool CustomMQTTDevice::publish(const std::string &topic, int value) {
   char buffer[24];
-  int len = snprintf(buffer, sizeof(buffer), "%d", value);
+  size_t len = buf_append_printf(buffer, sizeof(buffer), 0, "%d", value);
   return global_mqtt_client->publish(topic, buffer, len);
 }
 bool CustomMQTTDevice::publish_json(const std::string &topic, const json::json_build_t &f, uint8_t qos, bool retain) {
diff --git a/esphome/components/mqtt/mqtt_client.cpp b/esphome/components/mqtt/mqtt_client.cpp
index be3ac161476..7bec0f16901 100644
--- a/esphome/components/mqtt/mqtt_client.cpp
+++ b/esphome/components/mqtt/mqtt_client.cpp
@@ -94,9 +94,11 @@ void MQTTClientComponent::send_device_info_() {
             char key[8];  // "ip" + up to 3 digits + null
             char ip_buf[network::IP_ADDRESS_BUFFER_SIZE];
             if (index == 0) {
-              strcpy(key, "ip");
+              key[0] = 'i';
+              key[1] = 'p';
+              key[2] = '\0';
             } else {
-              snprintf(key, sizeof(key), "ip%u", index);
+              buf_append_printf(key, sizeof(key), 0, "ip%u", index);
             }
             ip.str_to(ip_buf);
             root[key] = ip_buf;
diff --git a/esphome/components/mqtt/mqtt_component.cpp b/esphome/components/mqtt/mqtt_component.cpp
index cfb8cc2ab69..419d51a8916 100644
--- a/esphome/components/mqtt/mqtt_component.cpp
+++ b/esphome/components/mqtt/mqtt_component.cpp
@@ -189,13 +189,15 @@ bool MQTTComponent::send_discovery_() {
         StringRef object_id = this->get_default_object_id_to_(object_id_buf);
         if (discovery_info.unique_id_generator == MQTT_MAC_ADDRESS_UNIQUE_ID_GENERATOR) {
           char friendly_name_hash[9];
-          snprintf(friendly_name_hash, sizeof(friendly_name_hash), "%08" PRIx32, fnv1_hash(this->friendly_name_()));
+          buf_append_printf(friendly_name_hash, sizeof(friendly_name_hash), 0, "%08" PRIx32,
+                            fnv1_hash(this->friendly_name_()));
           // Format: mac-component_type-hash (e.g. "aabbccddeeff-sensor-12345678")
           // MAC (12) + "-" (1) + domain (max 20) + "-" (1) + hash (8) + null (1) = 43
           char unique_id[MAC_ADDRESS_BUFFER_SIZE + ESPHOME_DOMAIN_MAX_LEN + 11];
           char mac_buf[MAC_ADDRESS_BUFFER_SIZE];
           get_mac_address_into_buffer(mac_buf);
-          snprintf(unique_id, sizeof(unique_id), "%s-%s-%s", mac_buf, this->component_type(), friendly_name_hash);
+          buf_append_printf(unique_id, sizeof(unique_id), 0, "%s-%s-%s", mac_buf, this->component_type(),
+                            friendly_name_hash);
           root[MQTT_UNIQUE_ID] = unique_id;
         } else {
           // default to almost-unique ID. It's a hack but the only way to get that
@@ -224,17 +226,14 @@ bool MQTTComponent::send_discovery_() {
             model == nullptr ? ESPHOME_PROJECT_NAME : std::string(ESPHOME_PROJECT_NAME, model - ESPHOME_PROJECT_NAME);
 #else
         static const char ver_fmt[] PROGMEM = ESPHOME_VERSION " (config hash 0x%08" PRIx32 ")";
-#ifdef USE_ESP8266
-        char fmt_buf[sizeof(ver_fmt)];
-        strcpy_P(fmt_buf, ver_fmt);
-        const char *fmt = fmt_buf;
-#else
-        const char *fmt = ver_fmt;
-#endif
         // Buffer sized for format string expansion: ~4 bytes net growth from format specifier to 8 hex digits, plus
         // safety margin
         char version_buf[sizeof(ver_fmt) + 8];
-        snprintf(version_buf, sizeof(version_buf), fmt, App.get_config_hash());
+#ifdef USE_ESP8266
+        snprintf_P(version_buf, sizeof(version_buf), ver_fmt, App.get_config_hash());
+#else
+        snprintf(version_buf, sizeof(version_buf), ver_fmt, App.get_config_hash());
+#endif
         device_info[MQTT_DEVICE_SW_VERSION] = version_buf;
         device_info[MQTT_DEVICE_MODEL] = ESPHOME_BOARD;
 #if defined(USE_ESP8266) || defined(USE_ESP32)
diff --git a/esphome/components/mqtt/mqtt_fan.cpp b/esphome/components/mqtt/mqtt_fan.cpp
index a6f05035888..0909090023b 100644
--- a/esphome/components/mqtt/mqtt_fan.cpp
+++ b/esphome/components/mqtt/mqtt_fan.cpp
@@ -175,7 +175,7 @@ bool MQTTFanComponent::publish_state() {
   auto traits = this->state_->get_traits();
   if (traits.supports_speed()) {
     char buf[12];
-    int len = snprintf(buf, sizeof(buf), "%d", this->state_->speed);
+    size_t len = buf_append_printf(buf, sizeof(buf), 0, "%d", this->state_->speed);
     bool success = this->publish(this->get_speed_level_state_topic(), buf, len);
     failed = failed || !success;
   }
diff --git a/esphome/components/mqtt/mqtt_number.cpp b/esphome/components/mqtt/mqtt_number.cpp
index 8342210ee41..471c0d12086 100644
--- a/esphome/components/mqtt/mqtt_number.cpp
+++ b/esphome/components/mqtt/mqtt_number.cpp
@@ -75,7 +75,7 @@ bool MQTTNumberComponent::send_initial_state() {
 }
 bool MQTTNumberComponent::publish_state(float value) {
   char buffer[64];
-  snprintf(buffer, sizeof(buffer), "%f", value);
+  buf_append_printf(buffer, sizeof(buffer), 0, "%f", value);
   return this->publish(this->get_state_topic_(), buffer);
 }