diff --git a/esphome/components/ble_nus/__init__.py b/esphome/components/ble_nus/__init__.py
index c0837da402..55a2f9bd18 100644
--- a/esphome/components/ble_nus/__init__.py
+++ b/esphome/components/ble_nus/__init__.py
@@ -7,6 +7,7 @@ from esphome.components.uart import (
     uart_ns,
 )
 from esphome.components.zephyr import zephyr_add_prj_conf
+from esphome.components.zephyr_ble_server import request_ble_l2cap_mtu
 import esphome.config_validation as cv
 from esphome.const import (
     CONF_DEBUG,
@@ -61,6 +62,7 @@ CONFIG_SCHEMA = cv.All(
 async def to_code(config: ConfigType) -> None:
     var = cg.new_Pvariable(config[CONF_ID])
     zephyr_add_prj_conf("BT_NUS", True)
+    request_ble_l2cap_mtu(247)  # DLE sweet spot: one NUS frame per LL PDU
     expose_log = config[CONF_TYPE] == CONF_LOGS
     cg.add(var.set_expose_log(expose_log))
     if expose_log:
diff --git a/esphome/components/zephyr_ble_server/__init__.py b/esphome/components/zephyr_ble_server/__init__.py
index a012e832c7..2493bd9f95 100644
--- a/esphome/components/zephyr_ble_server/__init__.py
+++ b/esphome/components/zephyr_ble_server/__init__.py
@@ -1,3 +1,5 @@
+from dataclasses import dataclass
+
 from esphome import automation
 import esphome.codegen as cg
 from esphome.components.nrf52.framework import (
@@ -7,9 +9,48 @@ from esphome.components.nrf52.framework import (
 from esphome.components.zephyr import zephyr_add_prj_conf
 import esphome.config_validation as cv
 from esphome.const import CONF_ID, Framework
-from esphome.core import CORE
+from esphome.core import CORE, CoroPriority, coroutine_with_priority
 from esphome.types import ConfigType
 
+# BLE LE Data Length Extension maximum LL PDU payload (BLE spec)
+_DLE_MAX_PDU = 251
+
+DOMAIN = "zephyr_ble_server"
+
+
+@dataclass
+class _BLEServerData:
+    requested_l2cap_mtu: int = 0
+    mtu_emitted: bool = False
+
+
+def _get_data() -> _BLEServerData:
+    if DOMAIN not in CORE.data:
+        CORE.data[DOMAIN] = _BLEServerData()
+    return CORE.data[DOMAIN]
+
+
+@coroutine_with_priority(CoroPriority.FINAL)
+async def _emit_ble_mtu() -> None:
+    data = _get_data()
+    data.mtu_emitted = True
+    mtu = data.requested_l2cap_mtu
+    if mtu > 0:
+        zephyr_add_prj_conf("BT_L2CAP_TX_MTU", mtu)
+        zephyr_add_prj_conf("BT_BUF_ACL_TX_SIZE", min(mtu + 4, _DLE_MAX_PDU))
+        zephyr_add_prj_conf("BT_BUF_ACL_RX_SIZE", mtu + 4)
+
+
+def request_ble_l2cap_mtu(l2cap_mtu: int) -> None:
+    """Request a minimum BLE L2CAP MTU. The maximum of all callers wins."""
+    data = _get_data()
+    if data.mtu_emitted:
+        raise RuntimeError("BLE L2CAP MTU requested after it was written to prj.conf")
+    if data.requested_l2cap_mtu == 0:
+        CORE.add_job(_emit_ble_mtu)
+    data.requested_l2cap_mtu = max(data.requested_l2cap_mtu, l2cap_mtu)
+
+
 zephyr_ble_server_ns = cg.esphome_ns.namespace("zephyr_ble_server")
 BLEServer = zephyr_ble_server_ns.class_("BLEServer", cg.Component)
 
@@ -51,6 +92,7 @@ async def to_code(config: ConfigType) -> None:
         zephyr_add_prj_conf("BT_SETTINGS", True)
         zephyr_add_prj_conf("BT_SMP_SC_ONLY", True)
         zephyr_add_prj_conf("BT_KEYS_OVERWRITE_OLDEST", True)
+        request_ble_l2cap_mtu(65)  # BT_SMP Kconfig default and range minimum
     await automation.build_callback_automations(var, config, _CALLBACK_AUTOMATIONS)
 
 
diff --git a/esphome/components/zephyr_mcumgr/ota/__init__.py b/esphome/components/zephyr_mcumgr/ota/__init__.py
index 109d1f7dd6..9fc02d8708 100644
--- a/esphome/components/zephyr_mcumgr/ota/__init__.py
+++ b/esphome/components/zephyr_mcumgr/ota/__init__.py
@@ -14,6 +14,7 @@ from esphome.components.zephyr.const import (
     KEY_BOOTLOADER,
     KEY_SYSBUILD,
 )
+from esphome.components.zephyr_ble_server import request_ble_l2cap_mtu
 import esphome.config_validation as cv
 from esphome.const import (
     CONF_HARDWARE_UART,
@@ -144,6 +145,7 @@ async def to_code(config: ConfigType) -> None:
         zephyr_add_prj_conf("MCUMGR_GRP_OS_MCUMGR_PARAMS", True)
 
         zephyr_add_prj_conf("NCS_SAMPLE_MCUMGR_BT_OTA_DFU_SPEEDUP", True)
+        request_ble_l2cap_mtu(498)  # matches NCS_SAMPLE_MCUMGR_BT_OTA_DFU_SPEEDUP
     if CONF_HARDWARE_UART in transport:
         uart = UARTS[transport[CONF_HARDWARE_UART]]
         uart_name = uart[0]
diff --git a/tests/component_tests/zephyr_ble_server/__init__.py b/tests/component_tests/zephyr_ble_server/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/tests/component_tests/zephyr_ble_server/config/no_request.yaml b/tests/component_tests/zephyr_ble_server/config/no_request.yaml
new file mode 100644
index 0000000000..dcf79033ec
--- /dev/null
+++ b/tests/component_tests/zephyr_ble_server/config/no_request.yaml
@@ -0,0 +1,8 @@
+esphome:
+  name: mtutest
+
+nrf52:
+  board: adafruit_itsybitsy_nrf52840
+  bootloader: adafruit_nrf52_sd140_v6
+
+zephyr_ble_server:
diff --git a/tests/component_tests/zephyr_ble_server/config/nus.yaml b/tests/component_tests/zephyr_ble_server/config/nus.yaml
new file mode 100644
index 0000000000..63129069d2
--- /dev/null
+++ b/tests/component_tests/zephyr_ble_server/config/nus.yaml
@@ -0,0 +1,11 @@
+esphome:
+  name: mtutest
+
+nrf52:
+  board: adafruit_itsybitsy_nrf52840
+  bootloader: adafruit_nrf52_sd140_v6
+
+logger:
+
+ble_nus:
+  type: logs
diff --git a/tests/component_tests/zephyr_ble_server/config/nus_mcumgr.yaml b/tests/component_tests/zephyr_ble_server/config/nus_mcumgr.yaml
new file mode 100644
index 0000000000..d62247dc54
--- /dev/null
+++ b/tests/component_tests/zephyr_ble_server/config/nus_mcumgr.yaml
@@ -0,0 +1,18 @@
+esphome:
+  name: mtutest
+
+nrf52:
+  board: adafruit_itsybitsy_nrf52840
+  bootloader: adafruit_nrf52_sd140_v6
+
+logger:
+
+zephyr_ble_server:
+
+ble_nus:
+  type: logs
+
+ota:
+  - platform: zephyr_mcumgr
+    transport:
+      ble: true
diff --git a/tests/component_tests/zephyr_ble_server/test_l2cap_mtu.py b/tests/component_tests/zephyr_ble_server/test_l2cap_mtu.py
new file mode 100644
index 0000000000..af0c4112b0
--- /dev/null
+++ b/tests/component_tests/zephyr_ble_server/test_l2cap_mtu.py
@@ -0,0 +1,52 @@
+"""Tests for the BLE L2CAP MTU that zephyr_ble_server writes to prj.conf."""
+
+from collections.abc import Callable
+from pathlib import Path
+
+import pytest
+
+from esphome.components.zephyr import zephyr_data
+from esphome.components.zephyr.const import KEY_PRJ_CONF
+from esphome.components.zephyr_ble_server import _emit_ble_mtu, request_ble_l2cap_mtu
+
+MTU_KEYS = (
+    "CONFIG_BT_L2CAP_TX_MTU",
+    "CONFIG_BT_BUF_ACL_TX_SIZE",
+    "CONFIG_BT_BUF_ACL_RX_SIZE",
+)
+
+
+def _mtu_values() -> tuple[int | None, ...]:
+    prj_conf = zephyr_data()[KEY_PRJ_CONF][""]
+    return tuple(prj_conf.get(key, (None,))[0] for key in MTU_KEYS)
+
+
+@pytest.mark.parametrize(
+    ("fixture", "expected"),
+    [
+        ("no_request.yaml", (None, None, None)),
+        ("nus.yaml", (247, 251, 251)),
+        # The largest request wins; only the TX buffer is capped at 251
+        ("nus_mcumgr.yaml", (498, 251, 502)),
+    ],
+)
+def test_l2cap_mtu_prj_conf(
+    fixture: str,
+    expected: tuple[int | None, ...],
+    generate_main: Callable[[str | Path], str],
+    component_config_path: Callable[[str], Path],
+) -> None:
+    generate_main(component_config_path(fixture))
+    assert _mtu_values() == expected
+
+
+@pytest.mark.asyncio
+async def test_request_after_emit_raises(
+    generate_main: Callable[[str | Path], str],
+    component_config_path: Callable[[str], Path],
+) -> None:
+    generate_main(component_config_path("no_request.yaml"))
+    request_ble_l2cap_mtu(247)
+    await _emit_ble_mtu()
+    with pytest.raises(RuntimeError, match="after it was written"):
+        request_ble_l2cap_mtu(498)