diff --git a/homeassistant/components/simplisafe/config_flow.py b/homeassistant/components/simplisafe/config_flow.py
index 93a2e152ad8..ad9614c0546 100644
--- a/homeassistant/components/simplisafe/config_flow.py
+++ b/homeassistant/components/simplisafe/config_flow.py
@@ -126,7 +126,8 @@ class SimpliSafeFlowHandler(config_entries.ConfigFlow, domain=DOMAIN):
             if existing_entries := [
                 entry
                 for entry in self.hass.config_entries.async_entries()
-                if entry.unique_id in (self._username, user_id)
+                if entry.domain == DOMAIN
+                and entry.unique_id in (self._username, user_id)
             ]:
                 existing_entry = existing_entries[0]
                 self.hass.config_entries.async_update_entry(
diff --git a/tests/components/simplisafe/test_config_flow.py b/tests/components/simplisafe/test_config_flow.py
index 91274f8f0c5..a4ef98e0e09 100644
--- a/tests/components/simplisafe/test_config_flow.py
+++ b/tests/components/simplisafe/test_config_flow.py
@@ -12,6 +12,8 @@ from homeassistant.const import CONF_CODE, CONF_TOKEN, CONF_USERNAME
 
 from .common import REFRESH_TOKEN, USER_ID, USERNAME
 
+from tests.common import MockConfigEntry
+
 CONF_USER_ID = "user_id"
 
 
@@ -57,9 +59,15 @@ async def test_options_flow(hass, config_entry):
 
 @pytest.mark.parametrize("unique_id", [USERNAME, USER_ID])
 async def test_step_reauth(
-    hass, config, config_entry, reauth_config, setup_simplisafe, sms_config
+    hass, config, config_entry, reauth_config, setup_simplisafe, sms_config, unique_id
 ):
     """Test the re-auth step (testing both username and user ID as unique ID)."""
+    # Add a second config entry (tied to a random domain, but with the same unique ID
+    # that could exist in a SimpliSafe entry) to ensure that this reauth process only
+    # touches the SimpliSafe entry:
+    entry = MockConfigEntry(domain="random", unique_id=USERNAME, data={"some": "data"})
+    entry.add_to_hass(hass)
+
     result = await hass.config_entries.flow.async_init(
         DOMAIN, context={"source": SOURCE_REAUTH}, data=config
     )
@@ -78,11 +86,17 @@ async def test_step_reauth(
     assert result["type"] == data_entry_flow.RESULT_TYPE_ABORT
     assert result["reason"] == "reauth_successful"
 
-    assert len(hass.config_entries.async_entries()) == 1
+    assert len(hass.config_entries.async_entries()) == 2
+
+    # Test that the SimpliSafe config flow is updated:
     [config_entry] = hass.config_entries.async_entries(DOMAIN)
     assert config_entry.unique_id == USER_ID
     assert config_entry.data == config
 
+    # Test that the non-SimpliSafe config flow remains the same:
+    [config_entry] = hass.config_entries.async_entries("random")
+    assert config_entry == entry
+
 
 @pytest.mark.parametrize(
     "exc,error_string",