diff --git a/graphiti_core/graphiti.py b/graphiti_core/graphiti.py
index 8e58a5ae..86265f9d 100644
--- a/graphiti_core/graphiti.py
+++ b/graphiti_core/graphiti.py
@@ -158,7 +158,7 @@ class Graphiti:
             If not set, the Graphiti default is used.
         ensure_ascii : bool, optional
             Whether to escape non-ASCII characters in JSON serialization for prompts. Defaults to False.
-            Set to False to preserve non-ASCII characters (e.g., Korean, Japanese, Chinese) in their
+            Set as False to preserve non-ASCII characters (e.g., Korean, Japanese, Chinese) in their
             original form, making them readable in LLM logs and improving model understanding.
 
         Returns
diff --git a/graphiti_core/search/search_filters.py b/graphiti_core/search/search_filters.py
index 3a5d2f21..2213688b 100644
--- a/graphiti_core/search/search_filters.py
+++ b/graphiti_core/search/search_filters.py
@@ -28,6 +28,8 @@ class ComparisonOperator(Enum):
     less_than = '<'
     greater_than_equal = '>='
     less_than_equal = '<='
+    is_null = 'IS NULL'
+    is_not_null = 'IS NOT NULL'
 
 
 class DateFilter(BaseModel):
@@ -64,6 +66,19 @@ def node_search_filter_query_constructor(
     return filter_query, filter_params
 
 
+def date_filter_query_constructor(
+    value_name: str, param_name: str, operator: ComparisonOperator
+) -> str:
+    query = '(' + value_name + ' '
+
+    if operator == ComparisonOperator.is_null or operator == ComparisonOperator.is_not_null:
+        query += operator.value + ')'
+    else:
+        query += operator.value + ' ' + param_name + ')'
+
+    return query
+
+
 def edge_search_filter_query_constructor(
     filters: SearchFilters,
 ) -> tuple[str, dict[str, Any]]:
@@ -85,10 +100,16 @@ def edge_search_filter_query_constructor(
         valid_at_filter = '\nAND ('
         for i, or_list in enumerate(filters.valid_at):
             for j, date_filter in enumerate(or_list):
-                filter_params['valid_at_' + str(j)] = date_filter.date
+                if date_filter.comparison_operator not in [
+                    ComparisonOperator.is_null,
+                    ComparisonOperator.is_not_null,
+                ]:
+                    filter_params['valid_at_' + str(j)] = date_filter.date
 
             and_filters = [
-                '(e.valid_at ' + date_filter.comparison_operator.value + f' $valid_at_{j})'
+                date_filter_query_constructor(
+                    'e.valid_at', f'$valid_at_{j}', date_filter.comparison_operator
+                )
                 for j, date_filter in enumerate(or_list)
             ]
             and_filter_query = ''
@@ -110,10 +131,16 @@ def edge_search_filter_query_constructor(
         invalid_at_filter = ' AND ('
         for i, or_list in enumerate(filters.invalid_at):
             for j, date_filter in enumerate(or_list):
-                filter_params['invalid_at_' + str(j)] = date_filter.date
+                if date_filter.comparison_operator not in [
+                    ComparisonOperator.is_null,
+                    ComparisonOperator.is_not_null,
+                ]:
+                    filter_params['invalid_at_' + str(j)] = date_filter.date
 
             and_filters = [
-                '(e.invalid_at ' + date_filter.comparison_operator.value + f' $invalid_at_{j})'
+                date_filter_query_constructor(
+                    'e.invalid_at', f'$invalid_at_{j}', date_filter.comparison_operator
+                )
                 for j, date_filter in enumerate(or_list)
             ]
             and_filter_query = ''
@@ -135,10 +162,16 @@ def edge_search_filter_query_constructor(
         created_at_filter = ' AND ('
         for i, or_list in enumerate(filters.created_at):
             for j, date_filter in enumerate(or_list):
-                filter_params['created_at_' + str(j)] = date_filter.date
+                if date_filter.comparison_operator not in [
+                    ComparisonOperator.is_null,
+                    ComparisonOperator.is_not_null,
+                ]:
+                    filter_params['created_at_' + str(j)] = date_filter.date
 
             and_filters = [
-                '(e.created_at ' + date_filter.comparison_operator.value + f' $created_at_{j})'
+                date_filter_query_constructor(
+                    'e.created_at', f'$created_at_{j}', date_filter.comparison_operator
+                )
                 for j, date_filter in enumerate(or_list)
             ]
             and_filter_query = ''
@@ -160,10 +193,16 @@ def edge_search_filter_query_constructor(
         expired_at_filter = ' AND ('
         for i, or_list in enumerate(filters.expired_at):
             for j, date_filter in enumerate(or_list):
-                filter_params['expired_at_' + str(j)] = date_filter.date
+                if date_filter.comparison_operator not in [
+                    ComparisonOperator.is_null,
+                    ComparisonOperator.is_not_null,
+                ]:
+                    filter_params['expired_at_' + str(j)] = date_filter.date
 
             and_filters = [
-                '(e.expired_at ' + date_filter.comparison_operator.value + f' $expired_at_{j})'
+                date_filter_query_constructor(
+                    'e.expired_at', f'$expired_at_{j}', date_filter.comparison_operator
+                )
                 for j, date_filter in enumerate(or_list)
             ]
             and_filter_query = ''
diff --git a/pyproject.toml b/pyproject.toml
index d0b864ae..cf476ef6 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,7 +1,7 @@
 [project]
 name = "graphiti-core"
 description = "A temporal graph building library"
-version = "0.18.5"
+version = "0.18.6"
 authors = [
     { name = "Paul Paliychuk", email = "paul@getzep.com" },
     { name = "Preston Rasmussen", email = "preston@getzep.com" },
diff --git a/tests/test_graphiti_int.py b/tests/test_graphiti_int.py
index 165464ce..276191d0 100644
--- a/tests/test_graphiti_int.py
+++ b/tests/test_graphiti_int.py
@@ -65,7 +65,11 @@ async def test_graphiti_init(driver):
 
     search_filter = SearchFilters(
         node_labels=['Person', 'City'],
-        created_at=[[DateFilter(date=utc_now(), comparison_operator=ComparisonOperator.less_than)]],
+        created_at=[
+            [DateFilter(date=None, comparison_operator=ComparisonOperator.is_null)],
+            [DateFilter(date=utc_now(), comparison_operator=ComparisonOperator.less_than)],
+            [DateFilter(date=None, comparison_operator=ComparisonOperator.is_not_null)],
+        ],
     )
 
     results = await graphiti.search_(
diff --git a/uv.lock b/uv.lock
index d9d8d33c..0d3fcadb 100644
--- a/uv.lock
+++ b/uv.lock
@@ -746,7 +746,7 @@ wheels = [
 
 [[package]]
 name = "graphiti-core"
-version = "0.18.4"
+version = "0.18.6"
 source = { editable = "." }
 dependencies = [
     { name = "diskcache" },