diff --git a/homeassistant/components/tradfri/__init__.py b/homeassistant/components/tradfri/__init__.py
index cd6adbc5fef..2de40ab46e6 100644
--- a/homeassistant/components/tradfri/__init__.py
+++ b/homeassistant/components/tradfri/__init__.py
@@ -21,6 +21,7 @@ from homeassistant.helpers.event import async_track_time_interval
 
 from .const import CONF_GATEWAY_ID, CONF_IDENTITY, CONF_KEY, DOMAIN, LOGGER
 from .coordinator import TradfriDeviceDataUpdateCoordinator
+from .migration import migrate_device_identifier
 from .models import TradfriData
 
 PLATFORMS = [
@@ -39,6 +40,9 @@ async def async_setup_entry(
     entry: ConfigEntry,
 ) -> bool:
     """Create a gateway."""
+    # Migrate old integer device identifier to string, added in core-2022.7.0.
+    migrate_device_identifier(hass, entry)
+
     factory = await APIFactory.init(
         entry.data[CONF_HOST],
         psk_id=entry.data[CONF_IDENTITY],
@@ -151,7 +155,7 @@ def remove_stale_devices(
             if identifier[0] != DOMAIN:
                 continue
 
-            # The device id in the identifier is not copied from integer to string
+            # The device id in the identifier was not copied from integer to string
             # when setting entity device info. Copy here to make sure it's a string.
             _id = str(identifier[1])
 
diff --git a/homeassistant/components/tradfri/entity.py b/homeassistant/components/tradfri/entity.py
index 6d85a54e039..d76958a311a 100644
--- a/homeassistant/components/tradfri/entity.py
+++ b/homeassistant/components/tradfri/entity.py
@@ -59,7 +59,7 @@ class TradfriBaseEntity(CoordinatorEntity[TradfriDeviceDataUpdateCoordinator]):
 
         info = self._device.device_info
         self._attr_device_info = DeviceInfo(
-            identifiers={(DOMAIN, self._device_id)},
+            identifiers={(DOMAIN, str(self._device.id))},
             manufacturer=info.manufacturer,
             model=info.model_number,
             name=self._device.name,
diff --git a/homeassistant/components/tradfri/migration.py b/homeassistant/components/tradfri/migration.py
new file mode 100644
index 00000000000..1f70e3942a1
--- /dev/null
+++ b/homeassistant/components/tradfri/migration.py
@@ -0,0 +1,32 @@
+"""Provide migration tools for the Tradfri integration."""
+from homeassistant.config_entries import ConfigEntry
+from homeassistant.core import HomeAssistant, callback
+import homeassistant.helpers.device_registry as dr
+
+from .const import DOMAIN
+
+
+@callback
+def migrate_device_identifier(hass: HomeAssistant, config_entry: ConfigEntry) -> None:
+    """Migrate device identifier to new format."""
+    device_registry = dr.async_get(hass)
+    device_entries = dr.async_entries_for_config_entry(
+        device_registry, config_entry.entry_id
+    )
+
+    for device_entry in device_entries:
+        device_identifiers = set(device_entry.identifiers)
+
+        for identifier in device_entry.identifiers:
+            if identifier[0] == DOMAIN and isinstance(
+                identifier[1], int  # type: ignore[unreachable]
+            ):
+                device_identifiers.remove(identifier)  # type: ignore[unreachable]
+                # Copy pytradfri device id to string.
+                device_identifiers.add((DOMAIN, str(identifier[1])))
+                break
+
+        if device_identifiers != device_entry.identifiers:
+            device_registry.async_update_device(
+                device_entry.id, new_identifiers=device_identifiers
+            )
diff --git a/tests/components/tradfri/test_migration.py b/tests/components/tradfri/test_migration.py
new file mode 100644
index 00000000000..21e52859cd9
--- /dev/null
+++ b/tests/components/tradfri/test_migration.py
@@ -0,0 +1,43 @@
+"""Test the tradfri migration tools."""
+from unittest.mock import MagicMock
+
+from homeassistant.components.tradfri.const import DOMAIN
+from homeassistant.core import HomeAssistant
+import homeassistant.helpers.device_registry as dr
+
+from . import GATEWAY_ID
+
+from tests.common import MockConfigEntry
+
+
+async def test_migrate_device_identifier(
+    hass: HomeAssistant, mock_api_factory: MagicMock
+) -> None:
+    """Test migrate device identifier."""
+    entry = MockConfigEntry(
+        domain=DOMAIN,
+        data={
+            "host": "mock-host",
+            "identity": "mock-identity",
+            "key": "mock-key",
+            "gateway_id": GATEWAY_ID,
+        },
+    )
+    entry.add_to_hass(hass)
+    device_registry = dr.async_get(hass)
+    device_entry = device_registry.async_get_or_create(
+        config_entry_id=entry.entry_id,
+        identifiers={(DOMAIN, 1)},  # type: ignore[arg-type]
+    )
+
+    assert device_entry.identifiers == {(DOMAIN, 1)}  # type: ignore[comparison-overlap]
+
+    # FIXME: We need to mock the pytradfri device on the gateway.
+
+    assert await hass.config_entries.async_setup(entry.entry_id)
+    await hass.async_block_till_done()
+
+    migrated_device_entry = device_registry.async_get(device_entry.id)
+
+    assert migrated_device_entry
+    assert migrated_device_entry.identifiers == {(DOMAIN, "1")}