diff --git a/homeassistant/components/google_assistant_sdk/config_flow.py b/homeassistant/components/google_assistant_sdk/config_flow.py
index 6c010d39c43..466a11bfd3e 100644
--- a/homeassistant/components/google_assistant_sdk/config_flow.py
+++ b/homeassistant/components/google_assistant_sdk/config_flow.py
@@ -8,7 +8,12 @@ from typing import Any
 
 import voluptuous as vol
 
-from homeassistant.config_entries import SOURCE_REAUTH, ConfigFlowResult, OptionsFlow
+from homeassistant.config_entries import (
+    SOURCE_REAUTH,
+    SOURCE_RECONFIGURE,
+    ConfigFlowResult,
+    OptionsFlow,
+)
 from homeassistant.core import callback
 from homeassistant.helpers import config_entry_oauth2_flow
 
@@ -40,6 +45,12 @@ class OAuth2FlowHandler(
             "prompt": "consent",
         }
 
+    async def async_step_reconfigure(
+        self, user_input: dict[str, Any] | None = None
+    ) -> ConfigFlowResult:
+        """Handle a reconfiguration flow."""
+        return await self.async_step_user(user_input)
+
     async def async_step_reauth(
         self, entry_data: Mapping[str, Any]
     ) -> ConfigFlowResult:
@@ -60,6 +71,10 @@ class OAuth2FlowHandler(
             return self.async_update_reload_and_abort(
                 self._get_reauth_entry(), data=data
             )
+        if self.source == SOURCE_RECONFIGURE:
+            return self.async_update_reload_and_abort(
+                self._get_reconfigure_entry(), data=data
+            )
 
         return self.async_create_entry(
             title=DEFAULT_NAME,
diff --git a/homeassistant/components/google_assistant_sdk/strings.json b/homeassistant/components/google_assistant_sdk/strings.json
index f26fdd4a29c..be03cadb408 100644
--- a/homeassistant/components/google_assistant_sdk/strings.json
+++ b/homeassistant/components/google_assistant_sdk/strings.json
@@ -30,7 +30,8 @@
       "oauth_failed": "[%key:common::config_flow::abort::oauth2_failed%]",
       "already_configured": "[%key:common::config_flow::abort::already_configured_account%]",
       "already_in_progress": "[%key:common::config_flow::abort::already_in_progress%]",
-      "reauth_successful": "[%key:common::config_flow::abort::reauth_successful%]"
+      "reauth_successful": "[%key:common::config_flow::abort::reauth_successful%]",
+      "reconfigure_successful": "[%key:common::config_flow::abort::reconfigure_successful%]"
     },
     "create_entry": {
       "default": "[%key:common::config_flow::create_entry::authenticated%]"
diff --git a/tests/components/google_assistant_sdk/test_config_flow.py b/tests/components/google_assistant_sdk/test_config_flow.py
index c911a2a084d..dbecabdb35f 100644
--- a/tests/components/google_assistant_sdk/test_config_flow.py
+++ b/tests/components/google_assistant_sdk/test_config_flow.py
@@ -157,6 +157,62 @@ async def test_reauth(
     assert config_entry.data["token"].get("refresh_token") == "mock-refresh-token"
 
 
+@pytest.mark.usefixtures("current_request_with_host")
+async def test_reconfigure(
+    hass: HomeAssistant,
+    hass_client_no_auth: ClientSessionGenerator,
+    aioclient_mock: AiohttpClientMocker,
+    setup_credentials: None,
+    config_entry: MockConfigEntry,
+) -> None:
+    """Test the reconfiguration flow updates the existing config entry."""
+    config_entry.add_to_hass(hass)
+
+    result = await config_entry.start_reconfigure_flow(hass)
+
+    assert result["type"] is FlowResultType.EXTERNAL_STEP
+
+    state = config_entry_oauth2_flow._encode_jwt(
+        hass,
+        {
+            "flow_id": result["flow_id"],
+            "redirect_uri": "https://example.com/auth/external/callback",
+        },
+    )
+    assert result["url"] == (
+        f"{GOOGLE_AUTH_URI}?response_type=code&client_id={CLIENT_ID}"
+        "&redirect_uri=https://example.com/auth/external/callback"
+        f"&state={state}&scope=https://www.googleapis.com/auth/assistant-sdk-prototype"
+        "&access_type=offline&prompt=consent"
+    )
+    client = await hass_client_no_auth()
+    resp = await client.get(f"/auth/external/callback?code=abcd&state={state}")
+    assert resp.status == 200
+    assert resp.headers["content-type"] == "text/html; charset=utf-8"
+
+    aioclient_mock.post(
+        GOOGLE_TOKEN_URI,
+        json={
+            "refresh_token": "mock-refresh-token",
+            "access_token": "updated-access-token",
+            "type": "Bearer",
+            "expires_in": 60,
+        },
+    )
+
+    result = await hass.config_entries.flow.async_configure(result["flow_id"])
+
+    assert result.get("type") is FlowResultType.ABORT
+    assert result.get("reason") == "reconfigure_successful"
+
+    assert len(hass.config_entries.async_entries(DOMAIN)) == 1
+    assert config_entry.unique_id is None
+    assert "token" in config_entry.data
+    # Verify access token is refreshed
+    assert config_entry.data["token"].get("access_token") == "updated-access-token"
+    assert config_entry.data["token"].get("refresh_token") == "mock-refresh-token"
+
+
 @pytest.mark.usefixtures("current_request_with_host")
 async def test_single_instance_allowed(
     hass: HomeAssistant,