diff --git a/backend/app/api/board_groups.py b/backend/app/api/board_groups.py
index e6988186..c21b005e 100644
--- a/backend/app/api/board_groups.py
+++ b/backend/app/api/board_groups.py
@@ -15,6 +15,7 @@ from app.db import crud
 from app.db.pagination import paginate
 from app.db.session import get_session
 from app.models.agents import Agent
+from app.models.board_group_memory import BoardGroupMemory
 from app.models.board_groups import BoardGroup
 from app.models.boards import Board
 from app.models.gateways import Gateway
@@ -279,6 +280,9 @@ async def delete_board_group(
     await session.execute(
         update(Board).where(col(Board.board_group_id) == group_id).values(board_group_id=None)
     )
+    await session.execute(
+        delete(BoardGroupMemory).where(col(BoardGroupMemory.board_group_id) == group_id)
+    )
     await session.execute(delete(BoardGroup).where(col(BoardGroup.id) == group_id))
     await session.commit()
     return OkResponse()
diff --git a/backend/tests/test_board_groups_delete.py b/backend/tests/test_board_groups_delete.py
new file mode 100644
index 00000000..d904716e
--- /dev/null
+++ b/backend/tests/test_board_groups_delete.py
@@ -0,0 +1,43 @@
+from __future__ import annotations
+
+from dataclasses import dataclass, field
+from types import SimpleNamespace
+from typing import Any
+from uuid import uuid4
+
+import pytest
+
+from app.api import board_groups
+
+
+@dataclass
+class _FakeSession:
+    executed: list[Any] = field(default_factory=list)
+    committed: int = 0
+
+    async def execute(self, statement: Any) -> None:
+        self.executed.append(statement)
+
+    async def commit(self) -> None:
+        self.committed += 1
+
+
+@pytest.mark.asyncio
+async def test_delete_board_group_cleans_group_memory_first(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    group_id = uuid4()
+
+    async def _fake_require_group_access(*_args: Any, **_kwargs: Any) -> None:
+        return None
+
+    monkeypatch.setattr(board_groups, "_require_group_access", _fake_require_group_access)
+
+    session = _FakeSession()
+    ctx = SimpleNamespace(member=object())
+
+    await board_groups.delete_board_group(group_id=group_id, session=session, ctx=ctx)
+
+    statement_tables = [statement.table.name for statement in session.executed]
+    assert statement_tables == ["boards", "board_group_memory", "board_groups"]
+    assert session.committed == 1