diff --git a/mem0/vector_stores/chroma.py b/mem0/vector_stores/chroma.py
index ad8f5cf34..6bdc9a4bf 100644
--- a/mem0/vector_stores/chroma.py
+++ b/mem0/vector_stores/chroma.py
@@ -316,8 +316,32 @@ class ChromaDB(VectorStoreBase):
                     processed_filters.append(or_conditions[0])
             
             elif key == "$not":
-                # Handle NOT conditions - ChromaDB doesn't have direct NOT, so we'll skip for now
-                continue
+                negate_op = {
+                    "eq": "$ne", "ne": "$eq",
+                    "gt": "$lte", "gte": "$lt",
+                    "lt": "$gte", "lte": "$gt",
+                    "in": "$nin", "nin": "$in",
+                }
+                negated_per_group = []
+                for condition in value:
+                    negated_fields = []
+                    for sub_key, sub_value in condition.items():
+                        if isinstance(sub_value, dict):
+                            for op, val in sub_value.items():
+                                neg = negate_op.get(op)
+                                if neg:
+                                    negated_fields.append({sub_key: {neg: val}})
+                        else:
+                            negated_fields.append({sub_key: {"$ne": sub_value}})
+                    if len(negated_fields) > 1:
+                        negated_per_group.append({"$or": negated_fields})
+                    elif len(negated_fields) == 1:
+                        negated_per_group.append(negated_fields[0])
+
+                if len(negated_per_group) > 1:
+                    processed_filters.append({"$and": negated_per_group})
+                elif len(negated_per_group) == 1:
+                    processed_filters.append(negated_per_group[0])
                 
             else:
                 # Regular condition
diff --git a/tests/vector_stores/test_chroma.py b/tests/vector_stores/test_chroma.py
index f355a0580..9c43c24c8 100644
--- a/tests/vector_stores/test_chroma.py
+++ b/tests/vector_stores/test_chroma.py
@@ -252,6 +252,48 @@ def test_generate_where_clause_non_string_values():
     assert result == expected
 
 
+def test_generate_where_clause_not_single_equality():
+    """Test $not with a single equality condition."""
+    filters = {"$not": [{"status": "archived"}]}
+    result = ChromaDB._generate_where_clause(filters)
+    assert result == {"status": {"$ne": "archived"}}
+
+
+def test_generate_where_clause_not_multiple_conditions():
+    """Test $not with multiple conditions (OR semantics, negated to AND)."""
+    filters = {"$not": [{"status": "archived"}, {"type": "draft"}]}
+    result = ChromaDB._generate_where_clause(filters)
+    assert result == {"$and": [{"status": {"$ne": "archived"}}, {"type": {"$ne": "draft"}}]}
+
+
+def test_generate_where_clause_not_with_operators():
+    """Test $not negates comparison operators correctly."""
+    filters = {"$not": [{"count": {"gt": 5}}]}
+    result = ChromaDB._generate_where_clause(filters)
+    assert result == {"count": {"$lte": 5}}
+
+
+def test_generate_where_clause_not_in_to_nin():
+    """Test $not converts 'in' to $nin."""
+    filters = {"$not": [{"status": {"in": ["archived", "deleted"]}}]}
+    result = ChromaDB._generate_where_clause(filters)
+    assert result == {"status": {"$nin": ["archived", "deleted"]}}
+
+
+def test_generate_where_clause_not_multi_field_condition():
+    """Test $not with multi-field condition uses De Morgan's (AND -> OR)."""
+    filters = {"$not": [{"status": "archived", "type": "draft"}]}
+    result = ChromaDB._generate_where_clause(filters)
+    assert result == {"$or": [{"status": {"$ne": "archived"}}, {"type": {"$ne": "draft"}}]}
+
+
+def test_generate_where_clause_not_combined_with_other_filters():
+    """Test $not combined with regular filters."""
+    filters = {"user_id": "alice", "$not": [{"status": "archived"}]}
+    result = ChromaDB._generate_where_clause(filters)
+    assert result == {"$and": [{"user_id": {"$eq": "alice"}}, {"status": {"$ne": "archived"}}]}
+
+
 def test_chroma_config_accepts_default_tmp_path():
     """Test that ChromaDbConfig accepts the default /tmp/chroma path."""
     config = ChromaDbConfig(path="/tmp/chroma")