diff --git a/CHANGELOG.md b/CHANGELOG.md
index c4587044e4..9b188ddc34 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,7 @@ ENHANCEMENTS:
 
 BUG FIXES:
 * Fix error handling in airlock processor ([#4929](https://github.com/microsoft/AzureTRE/pull/4929))
+* Fix Health check can falsely return OK even if Cosmos is down or inaccessible. ([#4926](https://github.com/microsoft/AzureTRE/issues/4926))
 
 ## (0.28.0) (March 2, 2026)
 **BREAKING CHANGES**
diff --git a/api_app/_version.py b/api_app/_version.py
index 7923a95d33..57a322dfc2 100644
--- a/api_app/_version.py
+++ b/api_app/_version.py
@@ -1 +1 @@
-__version__ = "0.25.16"
+__version__ = "0.25.17"
diff --git a/api_app/services/health_checker.py b/api_app/services/health_checker.py
index a4d53067b0..34139e4df9 100644
--- a/api_app/services/health_checker.py
+++ b/api_app/services/health_checker.py
@@ -19,7 +19,8 @@ async def create_state_store_status() -> Tuple[StatusEnum, str]:
     message = ""
     try:
         container: ContainerProxy = await Database().get_container_proxy(STATE_STORE_RESOURCES_CONTAINER)
-        container.query_items("SELECT TOP 1 * FROM c")
+        async for _ in container.query_items("SELECT TOP 1 * FROM c", max_item_count=1):
+            break
     except exceptions.ServiceRequestError:
         status = StatusEnum.not_ok
         message = strings.STATE_STORE_ENDPOINT_NOT_RESPONDING
diff --git a/api_app/tests_ma/test_services/test_health_checker.py b/api_app/tests_ma/test_services/test_health_checker.py
index 6b1d955f89..c166514067 100644
--- a/api_app/tests_ma/test_services/test_health_checker.py
+++ b/api_app/tests_ma/test_services/test_health_checker.py
@@ -2,6 +2,7 @@
 from unittest.mock import AsyncMock, MagicMock
 import pytest
 from azure.core.exceptions import ServiceRequestError
+from azure.cosmos.exceptions import CosmosHttpResponseError
 from azure.servicebus.exceptions import ServiceBusConnectionError
 from mock import patch
 from models.schemas.status import StatusEnum
@@ -11,8 +12,36 @@
 pytestmark = pytest.mark.asyncio
 
 
-@patch("azure.cosmos.aio.ContainerProxy.query_items", return_value=AsyncMock())
-async def test_get_state_store_status_responding(_) -> None:
+class AsyncIterator:
+    def __init__(self, seq):
+        self.iter = iter(seq)
+
+    def __aiter__(self):
+        return self
+
+    async def __anext__(self):
+        try:
+            return next(self.iter)
+        except StopIteration:
+            raise StopAsyncIteration
+
+
+class AsyncIteratorWithError:
+    def __init__(self, exception):
+        self.exception = exception
+
+    def __aiter__(self):
+        return self
+
+    async def __anext__(self):
+        raise self.exception
+
+
+@patch("api.dependencies.database.Database.get_container_proxy")
+async def test_get_state_store_status_responding(get_container_proxy_mock) -> None:
+    container_mock = MagicMock()
+    container_mock.query_items.return_value = AsyncIterator([{"id": "item"}])
+    get_container_proxy_mock.return_value = container_mock
     status, message = await health_checker.create_state_store_status()
 
     assert status == StatusEnum.ok
@@ -39,6 +68,28 @@ async def test_get_state_store_status_other_exception(container_proxy_mock) -> N
     assert message == strings.UNSPECIFIED_ERROR
 
 
+@patch("api.dependencies.database.Database.get_container_proxy")
+async def test_get_state_store_status_cosmos_http_error(get_container_proxy_mock) -> None:
+    container_mock = MagicMock()
+    container_mock.query_items.return_value = AsyncIteratorWithError(CosmosHttpResponseError(message="some message"))
+    get_container_proxy_mock.return_value = container_mock
+    status, message = await health_checker.create_state_store_status()
+
+    assert status == StatusEnum.not_ok
+    assert message == strings.STATE_STORE_ENDPOINT_NOT_ACCESSIBLE
+
+
+@patch("api.dependencies.database.Database.get_container_proxy")
+async def test_get_state_store_status_service_request_error(get_container_proxy_mock) -> None:
+    container_mock = MagicMock()
+    container_mock.query_items.return_value = AsyncIteratorWithError(ServiceRequestError(message="some message"))
+    get_container_proxy_mock.return_value = container_mock
+    status, message = await health_checker.create_state_store_status()
+
+    assert status == StatusEnum.not_ok
+    assert message == strings.STATE_STORE_ENDPOINT_NOT_RESPONDING
+
+
 @patch("core.credentials.get_credential_async_context")
 @patch("services.health_checker.ServiceBusClient")
 async def test_get_service_bus_status_responding(service_bus_client_mock, get_credential_async_context) -> None:
@@ -127,17 +178,3 @@ async def test_get_resource_processor_status_other_exception(resource_processor_
 
     assert status == StatusEnum.not_ok
     assert message == strings.UNSPECIFIED_ERROR
-
-
-class AsyncIterator:
-    def __init__(self, seq):
-        self.iter = iter(seq)
-
-    def __aiter__(self):
-        return self
-
-    async def __anext__(self):
-        try:
-            return next(self.iter)
-        except StopIteration:
-            raise StopAsyncIteration