diff --git a/backend/serializers/participant_serializer.py b/backend/serializers/participant_serializer.py
index beb4dc42..1c866d90 100644
--- a/backend/serializers/participant_serializer.py
+++ b/backend/serializers/participant_serializer.py
@@ -31,7 +31,8 @@ class Meta:
         validate=[
             validate.Length(max=13),
             validate.Regexp("^[+]*[(]{0,1}[0-9]{1,4}[)]{0,1}[-\s\./0-9]*$"),
-        ]
+        ],
+        allow_none=True,
     )
     slack = fields.Str(
         validate=[validate.Length(max=21), validate.Regexp("^[a-z0-9][a-z0-9._-]*$")]
diff --git a/backend/tests/test_participants_list.py b/backend/tests/test_participants_list.py
index 273617a5..de8fb86e 100644
--- a/backend/tests/test_participants_list.py
+++ b/backend/tests/test_participants_list.py
@@ -45,6 +45,15 @@ def test_create_participant_when_logged_in(app, auth_client, new_participant):
         assert value in response
 
 
+def test_create_participant_wiht_none_as_phone(auth_client, new_participant):
+    new_participant["phone"] = None
+
+    rv = auth_client.post("/participants/", json=new_participant)
+    response = rv.get_json()
+    assert rv.status_code == HTTPStatus.CREATED
+    assert response["phone"] is None
+
+
 def test_try_create_participant_without_payload(auth_client):
     """Test try to create new participant without payload."""
     rv = auth_client.post("/participants/", json={})