diff --git a/packages/graphrag/graphrag/query/indexer_adapters.py b/packages/graphrag/graphrag/query/indexer_adapters.py
index 7119ad842c..a6ded1f9f7 100644
--- a/packages/graphrag/graphrag/query/indexer_adapters.py
+++ b/packages/graphrag/graphrag/query/indexer_adapters.py
@@ -221,5 +221,5 @@ def _filter_under_community_level(
 ) -> pd.DataFrame:
     return cast(
         "pd.DataFrame",
-        df[df.level <= community_level],
+        df[(df.level <= community_level) | df.level.isna()],
     )
diff --git a/tests/unit/query/test_indexer_adapters.py b/tests/unit/query/test_indexer_adapters.py
new file mode 100644
index 0000000000..2e4abdd2f9
--- /dev/null
+++ b/tests/unit/query/test_indexer_adapters.py
@@ -0,0 +1,44 @@
+# Copyright (c) 2024 Microsoft Corporation.
+# Licensed under the MIT License
+
+import pandas as pd
+
+from graphrag.query.indexer_adapters import _filter_under_community_level
+
+
+def test_filter_under_community_level_preserves_nan():
+    """Entities without community assignment (level=NaN) should be preserved."""
+    df = pd.DataFrame({"id": [1, 2, 3], "level": [0.0, float("nan"), 2.0]})
+    result = _filter_under_community_level(df, 2)
+    assert len(result) == 3
+    assert result["id"].tolist() == [1, 2, 3]
+
+
+def test_filter_under_community_level_filters_above_level():
+    """Entities with level above community_level should be filtered out."""
+    df = pd.DataFrame({"id": [1, 2, 3], "level": [0.0, 1.0, 3.0]})
+    result = _filter_under_community_level(df, 2)
+    assert len(result) == 2
+    assert result["id"].tolist() == [1, 2]
+
+
+def test_filter_under_community_level_all_below():
+    """All entities within the community level should be preserved."""
+    df = pd.DataFrame({"id": [1, 2], "level": [0.0, 1.0]})
+    result = _filter_under_community_level(df, 2)
+    assert len(result) == 2
+
+
+def test_filter_under_community_level_all_nan():
+    """When all levels are NaN (no community assignments), all entities should be preserved."""
+    df = pd.DataFrame({"id": [1, 2], "level": [float("nan"), float("nan")]})
+    result = _filter_under_community_level(df, 2)
+    assert len(result) == 2
+
+
+def test_filter_under_community_level_mixed_with_nan():
+    """Mix of NaN and above-threshold levels should preserve NaN and drop above-threshold."""
+    df = pd.DataFrame({"id": [1, 2, 3], "level": [0.0, float("nan"), 5.0]})
+    result = _filter_under_community_level(df, 2)
+    assert len(result) == 2
+    assert result["id"].tolist() == [1, 2]