diff --git a/.chronus/changes/python-alternate-type-test-2026-9-29-5-24-0.md b/.chronus/changes/python-alternate-type-test-2026-9-29-5-24-0.md
new file mode 100644
index 00000000000..0a37fb768e2
--- /dev/null
+++ b/.chronus/changes/python-alternate-type-test-2026-9-29-5-24-0.md
@@ -0,0 +1,7 @@
+---
+changeKind: internal
+packages:
+  - "@typespec/http-client-python"
+---
+
+Assert alternate-type responses are deserialized as `geojson.Feature` in sync and async mock API tests.
diff --git a/packages/http-client-python/tests/mock_api/azure/asynctests/test_azure_client_generator_core_alternate_type_async.py b/packages/http-client-python/tests/mock_api/azure/asynctests/test_azure_client_generator_core_alternate_type_async.py
index 30f453723e1..31f286792b5 100644
--- a/packages/http-client-python/tests/mock_api/azure/asynctests/test_azure_client_generator_core_alternate_type_async.py
+++ b/packages/http-client-python/tests/mock_api/azure/asynctests/test_azure_client_generator_core_alternate_type_async.py
@@ -34,6 +34,7 @@ async def test_external_type_get_model(client: AlternateTypeClient):
     """Test getting a Feature object with geometry, properties, and optional id fields."""
     result = await client.external_type.get_model()
 
+    assert isinstance(result, geojson.Feature)
     # Validate the response structure based on the TypeSpec example
     assert result.type == "Feature"
     assert result.geometry.type == "Point"
@@ -55,6 +56,7 @@ async def test_external_type_get_property(client: AlternateTypeClient):
     """Test getting a ModelWithFeatureProperty object with feature and additionalProperty fields."""
     result = await client.external_type.get_property()
 
+    assert isinstance(result.feature, geojson.Feature)
     # Validate the response structure based on the TypeSpec example
     assert result.feature.type == "Feature"
     assert result.feature.geometry.type == "Point"
diff --git a/packages/http-client-python/tests/mock_api/azure/test_azure_client_generator_core_alternate_type.py b/packages/http-client-python/tests/mock_api/azure/test_azure_client_generator_core_alternate_type.py
index c5ae3266c87..278333d1ceb 100644
--- a/packages/http-client-python/tests/mock_api/azure/test_azure_client_generator_core_alternate_type.py
+++ b/packages/http-client-python/tests/mock_api/azure/test_azure_client_generator_core_alternate_type.py
@@ -32,6 +32,7 @@ def test_external_type_get_model(client: AlternateTypeClient):
     """Test getting a Feature object with geometry, properties, and optional id fields."""
     result = client.external_type.get_model()
 
+    assert isinstance(result, geojson.Feature)
     # Validate the response structure based on the TypeSpec example
     assert result.type == "Feature"
     assert result.geometry.type == "Point"
@@ -51,6 +52,7 @@ def test_external_type_get_property(client: AlternateTypeClient):
     """Test getting a ModelWithFeatureProperty object with feature and additionalProperty fields."""
     result = client.external_type.get_property()
 
+    assert isinstance(result.feature, geojson.Feature)
     # Validate the response structure based on the TypeSpec example
     assert result.feature.type == "Feature"
     assert result.feature.geometry.type == "Point"