diff --git a/.chronus/changes/add-python-alternate-type-mock-api-test-2026-5-12-23-16-00.md b/.chronus/changes/add-python-alternate-type-mock-api-test-2026-5-12-23-16-00.md
new file mode 100644
index 00000000000..47ce56ebe73
--- /dev/null
+++ b/.chronus/changes/add-python-alternate-type-mock-api-test-2026-5-12-23-16-00.md
@@ -0,0 +1,7 @@
+---
+changeKind: internal
+packages:
+  - "@typespec/http-client-python"
+---
+
+Add sync and async mock API tests for the azure/client-generator-core/alternate-type Spector scenario
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
new file mode 100644
index 00000000000..b741d5bad9e
--- /dev/null
+++ b/packages/http-client-python/tests/mock_api/azure/asynctests/test_azure_client_generator_core_alternate_type_async.py
@@ -0,0 +1,55 @@
+# -------------------------------------------------------------------------
+# Copyright (c) Microsoft Corporation. All rights reserved.
+# Licensed under the MIT License. See License.txt in the project root for
+# license information.
+# --------------------------------------------------------------------------
+import geojson
+import pytest
+import pytest_asyncio
+from specs.azure.clientgenerator.core.alternatetype import aio, models
+
+FEATURE = geojson.Feature(
+    geometry=geojson.Point((-122.25, 37.87)),
+    properties={
+        "name": "A single point of interest",
+        "category": "landmark",
+        "elevation": 100,
+    },
+    id="feature-1",
+)
+
+
+@pytest_asyncio.fixture
+async def client():
+    async with aio.AlternateTypeClient() as client:
+        yield client
+
+
+@pytest.mark.asyncio
+async def test_get_model(client: aio.AlternateTypeClient):
+    result = await client.external_type.get_model()
+    assert result == FEATURE
+
+
+@pytest.mark.asyncio
+async def test_put_model(client: aio.AlternateTypeClient):
+    await client.external_type.put_model(FEATURE)
+
+
+@pytest.mark.asyncio
+async def test_get_property(client: aio.AlternateTypeClient):
+    result = await client.external_type.get_property()
+    assert result == models.ModelWithFeatureProperty(
+        feature=FEATURE,
+        additional_property="extra",
+    )
+
+
+@pytest.mark.asyncio
+async def test_put_property(client: aio.AlternateTypeClient):
+    await client.external_type.put_property(
+        models.ModelWithFeatureProperty(
+            feature=FEATURE,
+            additional_property="extra",
+        )
+    )
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
new file mode 100644
index 00000000000..47faf6332a8
--- /dev/null
+++ b/packages/http-client-python/tests/mock_api/azure/test_azure_client_generator_core_alternate_type.py
@@ -0,0 +1,50 @@
+# -------------------------------------------------------------------------
+# Copyright (c) Microsoft Corporation. All rights reserved.
+# Licensed under the MIT License. See License.txt in the project root for
+# license information.
+# --------------------------------------------------------------------------
+import geojson
+import pytest
+from specs.azure.clientgenerator.core.alternatetype import AlternateTypeClient, models
+
+FEATURE = geojson.Feature(
+    geometry=geojson.Point((-122.25, 37.87)),
+    properties={
+        "name": "A single point of interest",
+        "category": "landmark",
+        "elevation": 100,
+    },
+    id="feature-1",
+)
+
+
+@pytest.fixture
+def client():
+    with AlternateTypeClient() as client:
+        yield client
+
+
+def test_get_model(client: AlternateTypeClient):
+    result = client.external_type.get_model()
+    assert result == FEATURE
+
+
+def test_put_model(client: AlternateTypeClient):
+    client.external_type.put_model(FEATURE)
+
+
+def test_get_property(client: AlternateTypeClient):
+    result = client.external_type.get_property()
+    assert result == models.ModelWithFeatureProperty(
+        feature=FEATURE,
+        additional_property="extra",
+    )
+
+
+def test_put_property(client: AlternateTypeClient):
+    client.external_type.put_property(
+        models.ModelWithFeatureProperty(
+            feature=FEATURE,
+            additional_property="extra",
+        )
+    )