diff --git a/graphene/core/classtypes/objecttype.py b/graphene/core/classtypes/objecttype.py
index 2bcb5e68..c5559fab 100644
--- a/graphene/core/classtypes/objecttype.py
+++ b/graphene/core/classtypes/objecttype.py
@@ -80,7 +80,7 @@ class ObjectType(six.with_metaclass(ObjectTypeMeta, FieldsClassType)):
         if kwargs:
             for prop in list(kwargs):
                 try:
-                    if isinstance(getattr(self.__class__, prop), property):
+                    if isinstance(getattr(self.__class__, prop), property) or prop.startswith('_'):
                         setattr(self, prop, kwargs.pop(prop))
                 except AttributeError:
                     pass
diff --git a/graphene/core/classtypes/tests/test_objecttype.py b/graphene/core/classtypes/tests/test_objecttype.py
index c554dbbf..609975f2 100644
--- a/graphene/core/classtypes/tests/test_objecttype.py
+++ b/graphene/core/classtypes/tests/test_objecttype.py
@@ -55,6 +55,17 @@ def test_object_type_set_properties():
     assert h.write_prop == 'custom'
 
 
+def test_object_type_set_private_attributes():
+    class Human(ObjectType):
+        _private_state = None
+
+    h = Human(_private_state='custom')
+    assert h._private_state == 'custom'
+
+    with raises(TypeError):
+        Human(_other_private_state='My name')
+
+
 def test_object_type_container_invalid_kwarg():
     class Human(ObjectType):
         name = String()