diff --git a/homeassistant/components/trmnl/config_flow.py b/homeassistant/components/trmnl/config_flow.py
index 259742a7969..d3ec0d1ca87 100644
--- a/homeassistant/components/trmnl/config_flow.py
+++ b/homeassistant/components/trmnl/config_flow.py
@@ -9,7 +9,12 @@ from trmnl import TRMNLClient
 from trmnl.exceptions import TRMNLAuthenticationError, TRMNLError
 import voluptuous as vol
 
-from homeassistant.config_entries import SOURCE_REAUTH, ConfigFlow, ConfigFlowResult
+from homeassistant.config_entries import (
+    SOURCE_REAUTH,
+    SOURCE_RECONFIGURE,
+    ConfigFlow,
+    ConfigFlowResult,
+)
 from homeassistant.const import CONF_API_KEY
 from homeassistant.helpers.aiohttp_client import async_get_clientsession
 
@@ -24,7 +29,7 @@ class TRMNLConfigFlow(ConfigFlow, domain=DOMAIN):
     async def async_step_user(
         self, user_input: dict[str, Any] | None = None
     ) -> ConfigFlowResult:
-        """Handle a flow initialized by the user or reauth."""
+        """Handle a flow initialized by the user, reauth, or reconfigure."""
         errors: dict[str, str] = {}
         if user_input:
             session = async_get_clientsession(self.hass)
@@ -46,6 +51,12 @@ class TRMNLConfigFlow(ConfigFlow, domain=DOMAIN):
                         self._get_reauth_entry(),
                         data_updates={CONF_API_KEY: user_input[CONF_API_KEY]},
                     )
+                if self.source == SOURCE_RECONFIGURE:
+                    self._abort_if_unique_id_mismatch()
+                    return self.async_update_reload_and_abort(
+                        self._get_reconfigure_entry(),
+                        data_updates={CONF_API_KEY: user_input[CONF_API_KEY]},
+                    )
                 self._abort_if_unique_id_configured()
                 return self.async_create_entry(
                     title=user.name,
@@ -62,3 +73,9 @@ class TRMNLConfigFlow(ConfigFlow, domain=DOMAIN):
     ) -> ConfigFlowResult:
         """Perform reauth upon an API authentication error."""
         return await self.async_step_user()
+
+    async def async_step_reconfigure(
+        self, user_input: dict[str, Any] | None = None
+    ) -> ConfigFlowResult:
+        """Handle reconfiguration."""
+        return await self.async_step_user()
diff --git a/homeassistant/components/trmnl/quality_scale.yaml b/homeassistant/components/trmnl/quality_scale.yaml
index 8643a185146..29883927d6b 100644
--- a/homeassistant/components/trmnl/quality_scale.yaml
+++ b/homeassistant/components/trmnl/quality_scale.yaml
@@ -62,7 +62,7 @@ rules:
   entity-translations: done
   exception-translations: done
   icon-translations: done
-  reconfiguration-flow: todo
+  reconfiguration-flow: done
   repair-issues:
     status: exempt
     comment: There are no repairable issues
diff --git a/homeassistant/components/trmnl/strings.json b/homeassistant/components/trmnl/strings.json
index 4b35b6faec3..ea278acacc2 100644
--- a/homeassistant/components/trmnl/strings.json
+++ b/homeassistant/components/trmnl/strings.json
@@ -3,6 +3,7 @@
     "abort": {
       "already_configured": "[%key:common::config_flow::abort::already_configured_account%]",
       "reauth_successful": "[%key:common::config_flow::abort::reauth_successful%]",
+      "reconfigure_successful": "[%key:common::config_flow::abort::reconfigure_successful%]",
       "unique_id_mismatch": "The API key belongs to a different account. Please use the API key for the original account."
     },
     "error": {
diff --git a/tests/components/trmnl/test_config_flow.py b/tests/components/trmnl/test_config_flow.py
index 0609c375f45..f5aba709c16 100644
--- a/tests/components/trmnl/test_config_flow.py
+++ b/tests/components/trmnl/test_config_flow.py
@@ -92,9 +92,9 @@ async def test_duplicate_entry(
     assert result["reason"] == "already_configured"
 
 
+@pytest.mark.usefixtures("mock_trmnl_client", "mock_setup_entry")
 async def test_reauth_flow(
     hass: HomeAssistant,
-    mock_trmnl_client: AsyncMock,
     mock_config_entry: MockConfigEntry,
 ) -> None:
     """Test the reauth flow."""
@@ -124,6 +124,7 @@ async def test_reauth_flow(
 async def test_reauth_flow_errors(
     hass: HomeAssistant,
     mock_trmnl_client: AsyncMock,
+    mock_setup_entry: AsyncMock,
     mock_config_entry: MockConfigEntry,
     exception: type[Exception],
     error: str,
@@ -152,6 +153,7 @@ async def test_reauth_flow_errors(
     assert result["reason"] == "reauth_successful"
 
 
+@pytest.mark.usefixtures("mock_setup_entry")
 async def test_reauth_flow_wrong_account(
     hass: HomeAssistant,
     mock_trmnl_client: AsyncMock,
@@ -170,3 +172,85 @@ async def test_reauth_flow_wrong_account(
 
     assert result["type"] is FlowResultType.ABORT
     assert result["reason"] == "unique_id_mismatch"
+
+
+@pytest.mark.usefixtures("mock_trmnl_client", "mock_setup_entry")
+async def test_reconfigure_flow(
+    hass: HomeAssistant,
+    mock_config_entry: MockConfigEntry,
+) -> None:
+    """Test the reconfigure flow."""
+    mock_config_entry.add_to_hass(hass)
+
+    result = await mock_config_entry.start_reconfigure_flow(hass)
+    assert result["type"] is FlowResultType.FORM
+    assert result["step_id"] == "user"
+
+    result = await hass.config_entries.flow.async_configure(
+        result["flow_id"], {CONF_API_KEY: "user_bbbbbbbbbb"}
+    )
+
+    assert result["type"] is FlowResultType.ABORT
+    assert result["reason"] == "reconfigure_successful"
+    assert mock_config_entry.data == {CONF_API_KEY: "user_bbbbbbbbbb"}
+
+
+@pytest.mark.parametrize(
+    ("exception", "error"),
+    [
+        (TRMNLAuthenticationError, "invalid_auth"),
+        (TRMNLError, "cannot_connect"),
+        (Exception, "unknown"),
+    ],
+)
+async def test_reconfigure_flow_errors(
+    hass: HomeAssistant,
+    mock_trmnl_client: AsyncMock,
+    mock_setup_entry: AsyncMock,
+    mock_config_entry: MockConfigEntry,
+    exception: type[Exception],
+    error: str,
+) -> None:
+    """Test reconfigure flow error handling."""
+    mock_config_entry.add_to_hass(hass)
+
+    result = await mock_config_entry.start_reconfigure_flow(hass)
+
+    mock_trmnl_client.get_me.side_effect = exception
+
+    result = await hass.config_entries.flow.async_configure(
+        result["flow_id"], {CONF_API_KEY: "user_bbbbbbbbbb"}
+    )
+
+    assert result["type"] is FlowResultType.FORM
+    assert result["errors"] == {"base": error}
+
+    mock_trmnl_client.get_me.side_effect = None
+
+    result = await hass.config_entries.flow.async_configure(
+        result["flow_id"], {CONF_API_KEY: "user_bbbbbbbbbb"}
+    )
+
+    assert result["type"] is FlowResultType.ABORT
+    assert result["reason"] == "reconfigure_successful"
+
+
+@pytest.mark.usefixtures("mock_setup_entry")
+async def test_reconfigure_flow_wrong_account(
+    hass: HomeAssistant,
+    mock_trmnl_client: AsyncMock,
+    mock_config_entry: MockConfigEntry,
+) -> None:
+    """Test reconfigure aborts when the API key belongs to a different account."""
+    mock_config_entry.add_to_hass(hass)
+
+    result = await mock_config_entry.start_reconfigure_flow(hass)
+
+    mock_trmnl_client.get_me.return_value.identifier = 99999
+
+    result = await hass.config_entries.flow.async_configure(
+        result["flow_id"], {CONF_API_KEY: "user_cccccccccc"}
+    )
+
+    assert result["type"] is FlowResultType.ABORT
+    assert result["reason"] == "unique_id_mismatch"