diff --git a/homeassistant/components/tag/trigger.py b/homeassistant/components/tag/trigger.py
index 6827448f4dbd..ff4bc2ac2daf 100644
--- a/homeassistant/components/tag/trigger.py
+++ b/homeassistant/components/tag/trigger.py
@@ -4,7 +4,7 @@ import voluptuous as vol
 
 from homeassistant.const import CONF_PLATFORM
 from homeassistant.core import CALLBACK_TYPE, Event, HassJob, HomeAssistant
-from homeassistant.helpers import config_validation as cv
+from homeassistant.helpers import config_validation as cv, device_registry as dr
 from homeassistant.helpers.trigger import TriggerActionType, TriggerInfo
 from homeassistant.helpers.typing import ConfigType
 
@@ -31,6 +31,18 @@ async def async_attach_trigger(
     device_ids: set[str] | None = (
         set(config[DEVICE_ID]) if DEVICE_ID in config else None
     )
+    if device_ids is not None:
+        device_registry = dr.async_get(hass)
+        # A pre-migration composite device id no longer refers to a registered device;
+        # a tag scanned event carries the id of one of the devices it was split into.
+        # Expand it to those split device ids so the trigger keeps matching.
+        for device_id in list(device_ids):
+            split_devices = device_registry.async_get_devices_for_composite_device_id(
+                device_id
+            )
+            if split_devices:
+                device_ids.discard(device_id)
+                device_ids.update(split_device.id for split_device in split_devices)
 
     job = HassJob(action)
 
diff --git a/tests/components/tag/test_trigger.py b/tests/components/tag/test_trigger.py
index 91f1bfba95b1..1e26427d0f8b 100644
--- a/tests/components/tag/test_trigger.py
+++ b/tests/components/tag/test_trigger.py
@@ -2,6 +2,7 @@
 
 from typing import Any
 
+import attr
 import pytest
 
 from homeassistant.components import automation
@@ -9,8 +10,11 @@ from homeassistant.components.tag import async_scan_tag
 from homeassistant.components.tag.const import DEVICE_ID, DOMAIN, TAG_ID
 from homeassistant.const import ATTR_ENTITY_ID, SERVICE_TURN_OFF
 from homeassistant.core import HomeAssistant, ServiceCall
+from homeassistant.helpers import device_registry as dr
 from homeassistant.setup import async_setup_component
 
+from tests.common import MockConfigEntry
+
 
 @pytest.fixture
 def tag_setup(hass: HomeAssistant, hass_storage: dict[str, Any]):
@@ -151,3 +155,87 @@ async def test_multiple_tags_and_devices_trigger(
     assert service_calls[1].data["message"] == "service called"
     assert service_calls[2].data["message"] == "service called"
     assert service_calls[3].data["message"] == "service called"
+
+
+COMPOSITE_ID = "composite00000000000000000000ab"
+
+
+@pytest.fixture
+def split_devices(
+    hass: HomeAssistant, device_registry: dr.DeviceRegistry
+) -> tuple[dr.DeviceEntry, dr.DeviceEntry]:
+    """Create two devices which are splits of a pre-migration composite device."""
+    entry_1 = MockConfigEntry(domain="itg1")
+    entry_1.add_to_hass(hass)
+    entry_2 = MockConfigEntry(domain="itg2")
+    entry_2.add_to_hass(hass)
+    device_1 = device_registry.async_get_or_create(
+        config_entry_id=entry_1.entry_id,
+        identifiers={("itg1", "1")},
+        name="Split device 1",
+    )
+    device_2 = device_registry.async_get_or_create(
+        config_entry_id=entry_2.entry_id,
+        identifiers={("itg2", "1")},
+        name="Split device 2",
+    )
+    device_registry._devices[device_1.id] = attr.evolve(
+        device_1, composite_device_id=COMPOSITE_ID
+    )
+    device_registry._devices[device_2.id] = attr.evolve(
+        device_2, composite_device_id=COMPOSITE_ID
+    )
+    return device_registry._devices[device_1.id], device_registry._devices[device_2.id]
+
+
+async def test_composite_device_trigger(
+    hass: HomeAssistant,
+    tag_setup,
+    service_calls: list[ServiceCall],
+    split_devices: tuple[dr.DeviceEntry, dr.DeviceEntry],
+) -> None:
+    """Test a tag trigger configured with a pre-migration composite device id.
+
+    The composite device id no longer refers to a registered device; it is expanded to
+    the ids of the devices it was split into, so a tag scanned by either split device
+    fires the trigger.
+    """
+    device_1, device_2 = split_devices
+    assert await tag_setup()
+    assert await async_setup_component(
+        hass,
+        automation.DOMAIN,
+        {
+            automation.DOMAIN: [
+                {
+                    "trigger": {
+                        "platform": DOMAIN,
+                        TAG_ID: "abc123",
+                        DEVICE_ID: COMPOSITE_ID,
+                    },
+                    "action": {
+                        "service": "test.automation",
+                        "data": {"message": "service called"},
+                    },
+                }
+            ]
+        },
+    )
+
+    await hass.async_block_till_done()
+
+    # A scan by the composite id or an unrelated device should not fire
+    await async_scan_tag(hass, tag_id="abc123", device_id=COMPOSITE_ID)
+    await async_scan_tag(hass, tag_id="abc123", device_id="other_device")
+    await hass.async_block_till_done()
+    assert len(service_calls) == 0
+
+    # A scan by either split device should fire
+    await async_scan_tag(hass, tag_id="abc123", device_id=device_1.id)
+    await hass.async_block_till_done()
+    await async_scan_tag(hass, tag_id="abc123", device_id=device_2.id)
+    await hass.async_block_till_done()
+
+    assert len(service_calls) == 2
+    assert service_calls[0].data["message"] == "service called"
+    assert service_calls[1].data["message"] == "service called"