diff --git a/bigquery/google/cloud/bigquery/_helpers.py b/bigquery/google/cloud/bigquery/_helpers.py
index 98eadb0a2f8e..21a8e3636d24 100644
--- a/bigquery/google/cloud/bigquery/_helpers.py
+++ b/bigquery/google/cloud/bigquery/_helpers.py
@@ -424,11 +424,12 @@ def _record_field_to_json(fields, row_value):
 
     for subindex, subfield in enumerate(fields):
         subname = subfield.name
-        if isdict:
-            subvalue = row_value.get(subname)
-        else:
-            subvalue = row_value[subindex]
-        record[subname] = _field_to_json(subfield, subvalue)
+        subvalue = row_value.get(subname) if isdict else row_value[subindex]
+
+        # None values are unconditionally omitted
+        if subvalue is not None:
+            record[subname] = _field_to_json(subfield, subvalue)
+
     return record
 
 
diff --git a/bigquery/tests/unit/test__helpers.py b/bigquery/tests/unit/test__helpers.py
index 6d92b4de73ba..fa6d27c981d8 100644
--- a/bigquery/tests/unit/test__helpers.py
+++ b/bigquery/tests/unit/test__helpers.py
@@ -856,14 +856,39 @@ def test_w_non_empty_dict(self):
         converted = self._call_fut(fields, original)
         self.assertEqual(converted, {"one": "42", "two": "two"})
 
-    def test_w_missing_nullable(self):
+    def test_w_some_missing_nullables(self):
         fields = [
             _make_field("INT64", name="one", mode="NULLABLE"),
             _make_field("STRING", name="two", mode="NULLABLE"),
         ]
         original = {"one": 42}
         converted = self._call_fut(fields, original)
-        self.assertEqual(converted, {"one": "42", "two": None})
+
+        # missing fields should not be converted to an explicit None
+        self.assertEqual(converted, {"one": "42"})
+
+    def test_w_all_missing_nullables(self):
+        fields = [
+            _make_field("INT64", name="one", mode="NULLABLE"),
+            _make_field("STRING", name="two", mode="NULLABLE"),
+        ]
+        original = {}
+        converted = self._call_fut(fields, original)
+
+        # we should get an empty dict, not None
+        self.assertEqual(converted, {})
+
+    def test_w_explicit_none_value(self):
+        fields = [
+            _make_field("INT64", name="one", mode="NULLABLE"),
+            _make_field("STRING", name="two", mode="NULLABLE"),
+            _make_field("BOOL", name="three", mode="REPEATED"),
+        ]
+        original = {"three": None, "one": 42, "two": None}
+        converted = self._call_fut(fields, original)
+
+        # None values should be dropped regardless of the field type
+        self.assertEqual(converted, {"one": "42"})
 
 
 class Test_field_to_json(unittest.TestCase):
diff --git a/bigquery/tests/unit/test_client.py b/bigquery/tests/unit/test_client.py
index cce4bc532074..f20e774d0867 100644
--- a/bigquery/tests/unit/test_client.py
+++ b/bigquery/tests/unit/test_client.py
@@ -4636,10 +4636,13 @@ def test_insert_rows_w_schema(self):
         ]
 
         def _row_data(row):
+            result = {"full_name": row[0], "age": str(row[1])}
             joined = row[2]
-            if isinstance(row[2], datetime.datetime):
+            if isinstance(joined, datetime.datetime):
                 joined = _microseconds_from_datetime(joined) * 1e-6
-            return {"full_name": row[0], "age": str(row[1]), "joined": joined}
+            if joined is not None:
+                result["joined"] = joined
+            return result
 
         SENT = {
             "rows": [
@@ -4708,7 +4711,10 @@ def test_insert_rows_w_list_of_dictionaries(self):
 
         def _row_data(row):
             joined = row["joined"]
-            if isinstance(joined, datetime.datetime):
+            if joined is None:
+                row = copy.deepcopy(row)
+                del row["joined"]
+            elif isinstance(joined, datetime.datetime):
                 row["joined"] = _microseconds_from_datetime(joined) * 1e-6
             row["age"] = str(row["age"])
             return row
@@ -4927,9 +4933,8 @@ def test_insert_rows_w_repeated_fields(self):
                 },
                 {
                     "json": {
-                        "color": None,
                         "items": [],
-                        "structs": [{"score": None, "times": [], "distances": [3.5]}],
+                        "structs": [{"times": [], "distances": [3.5]}],
                     },
                     "insertId": "1",
                 },
@@ -4996,10 +5001,7 @@ def test_insert_rows_w_record_schema(self):
                     },
                     "insertId": "1",
                 },
-                {
-                    "json": {"full_name": "Wylma Phlyntstone", "phone": None},
-                    "insertId": "2",
-                },
+                {"json": {"full_name": "Wylma Phlyntstone"}, "insertId": "2"},
             ]
         }