diff --git a/cadasta/organization/forms.py b/cadasta/organization/forms.py
index ce23b8ba5..98708fd05 100644
--- a/cadasta/organization/forms.py
+++ b/cadasta/organization/forms.py
@@ -127,6 +127,12 @@ def clean_identifier(self):
                 identifier=identifier)
         except (User.DoesNotExist, User.MultipleObjectsReturned) as e:
             raise forms.ValidationError(e)
+        num_roles = OrganizationRole.objects.filter(
+            user=self.user, organization=self.organization).count()
+        if num_roles != 0:
+            raise forms.ValidationError(
+                _("User is already a member of the organization."),
+                code='member_already')
 
     def save(self):
         if self.errors:
@@ -136,9 +142,7 @@ def save(self):
             )
 
         self.instance = OrganizationRole.objects.create(
-            user=self.user,
-            organization=self.organization
-        )
+            organization=self.organization, user=self.user)
         return self.instance
 
 
diff --git a/cadasta/organization/tests/test_forms.py b/cadasta/organization/tests/test_forms.py
index 28614e021..7ad533a5a 100644
--- a/cadasta/organization/tests/test_forms.py
+++ b/cadasta/organization/tests/test_forms.py
@@ -129,23 +129,27 @@ def test_remove_all_contacts(self):
 
 
 class AddOrganizationMemberFormTest(UserTestCase):
+    def setUp(self):
+        super().setUp()
+        self.org = OrganizationFactory.create()
+        self.user = UserFactory.create()
+
     def _save(self, identifier=None, identifier_field=None, ok=True):
-        org = OrganizationFactory.create()
-        user = UserFactory.create()
         if identifier_field is not None:
-            identifier = getattr(user, identifier_field)
+            identifier = getattr(self.user, identifier_field)
         data = {'identifier': identifier}
-        form = forms.AddOrganizationMemberForm(data, organization=org)
+        form = forms.AddOrganizationMemberForm(data, organization=self.org)
+        num_roles_before = len(OrganizationRole.objects.all())
         if ok:
             form.save()
             assert form.is_valid() is True
             assert OrganizationRole.objects.filter(
-                organization=org, user=user).count() == 1
+                organization=self.org, user=self.user).count() == 1
         else:
             with raises(ValueError):
                 form.save()
             assert form.is_valid() is False
-            assert OrganizationRole.objects.count() == 0
+            assert OrganizationRole.objects.count() == num_roles_before
 
     def test_add_with_username(self):
         self._save(identifier_field='username')
@@ -156,6 +160,11 @@ def test_add_with_email(self):
     def test_add_non_existing_user(self):
         self._save(identifier='some-user', ok=False)
 
+    def test_add_already_member_user(self):
+        OrganizationRole.objects.create(
+            organization=self.org, user=self.user)
+        self._save(identifier_field='username', ok=False)
+
 
 class EditOrganizationMemberFormTest(UserTestCase):
     def test_edit_org_role(self):
diff --git a/functional_tests/organizations/test_organization_member_list.py b/functional_tests/organizations/test_organization_member_list.py
index e2deae89a..2ac300ae9 100644
--- a/functional_tests/organizations/test_organization_member_list.py
+++ b/functional_tests/organizations/test_organization_member_list.py
@@ -59,6 +59,13 @@ def test_adding_members(self):
         error_message = 'User with username or email darthvader does not exist'
         assert error_list == error_message
 
+        input_box = page.click_on_input()
+        input_box.clear()
+        input_box.send_keys("admin_user")
+        error_list = page.click_submit_button(success=False)
+        error_message = 'User is already a member of the organization.'
+        assert error_list == error_message
+
         input_box = page.click_on_input()
         input_box.clear()
         input_box.send_keys("hansolo")