diff --git a/backend/auth/models.py b/backend/auth/models.py
index 4a2a359..49e42f8 100644
--- a/backend/auth/models.py
+++ b/backend/auth/models.py
@@ -1,9 +1,10 @@
-from sqlalchemy import Column, Integer, String, ForeignKey, Boolean, Enum, Table
-from sqlalchemy.orm import backref, relationship
+from sqlalchemy import Column, Integer, String, ForeignKey, Boolean, Enum, text
+from sqlalchemy.event import listens_for
+from sqlalchemy.orm import relationship
 from sqlalchemy.sql.schema import UniqueConstraint
 
-from ..base_models import Base
 from .enum import RecipientType, PermissionTargetType, PermissionType
+from ..base_models import Base
 
 
 class Group(Base):
@@ -104,3 +105,22 @@ class UserGroup(Base):
     __table_args__ = (
         UniqueConstraint('user_id', 'group_id'),
     )
+
+
+def delete_dangling_permissions(connection, recipient_type: RecipientType, recipient_id: int):
+    connection.execute(
+        text("DELETE FROM permissions WHERE recipient_type = :type AND recipient_id = :id"),
+        {"type": recipient_type.name, "id": recipient_id}
+    )
+
+
+# Since permissions table doesn't relate to its recipient tables we can't use sqlalchemy's cascade
+# setting, but we have to delete those manually using event listeners.
+@listens_for(User, "after_delete")
+def delete_dangling_user_permissions(_, connection, target):
+    delete_dangling_permissions(connection, RecipientType.USER, target.id)
+
+
+@listens_for(Group, "after_delete")
+def delete_dangling_group_permissions(_, connection, target):
+    delete_dangling_permissions(connection, RecipientType.GROUP, target.id)
diff --git a/backend/tests/test_crud_auth.py b/backend/tests/test_crud_auth.py
index 633921f..6681d5f 100644
--- a/backend/tests/test_crud_auth.py
+++ b/backend/tests/test_crud_auth.py
@@ -295,7 +295,6 @@ def test_has_permission(self, dbsession: Session, testuser: User):
         add_members(su_testgroup.id, [other_user.id], dbsession)
 
         assert has_permission(other_user, req_perm, dbsession) is True
-        
 
     def test_revoke_permission(self, dbsession: Session):
         user, group, parent_group = self._create_user_group_with_perm(dbsession)
@@ -320,3 +319,28 @@ def test_revoke_permission__not_existent(self, dbsession: Session):
         result = revoke_permissions([9999], dbsession)
         assert result is False
         assert dbsession.query(Permission.id).count() == 5
+
+    @pytest.mark.parametrize(["recipient_type", "attr_name"], [
+        (RecipientType.USER.name, 'user'),
+        (RecipientType.GROUP.name, 'group'),
+    ])
+    def test_cascade_delete_permissions(self, dbsession: Session, recipient_type, attr_name):
+        user, group, _ = self._create_user_group_with_perm(dbsession)
+
+        permissions_count = (
+            dbsession.query(Permission)
+            .filter_by(recipient_type=recipient_type, recipient_id=locals().get(attr_name).id)
+            .count()
+        )
+        assert permissions_count > 0
+
+        dbsession.delete(locals().get(attr_name))
+        dbsession.commit()
+
+        permissions_count = (
+            dbsession.query(Permission)
+            .filter_by(recipient_type=recipient_type, recipient_id=locals().get(attr_name).id)
+            .count()
+        )
+        assert permissions_count == 0
+