diff --git a/atst/domain/workspaces.py b/atst/domain/workspaces.py
index 3997ab9f..cd161267 100644
--- a/atst/domain/workspaces.py
+++ b/atst/domain/workspaces.py
@@ -1,7 +1,7 @@
 from sqlalchemy.orm.exc import NoResultFound
 
 from atst.database import db
-from atst.domain.exceptions import NotFoundError
+from atst.domain.exceptions import NotFoundError, UnauthorizedError
 from atst.models.workspace import Workspace
 from atst.models.workspace_role import WorkspaceRole
 from atst.domain.roles import Roles
@@ -27,12 +27,15 @@ class Workspaces(object):
         return workspace
 
     @classmethod
-    def get(cls, workspace_id):
+    def get(cls, user, workspace_id):
         try:
             workspace = db.session.query(Workspace).filter_by(id=workspace_id).one()
         except NoResultFound:
             raise NotFoundError("workspace")
 
+        if user not in workspace.users:
+            raise UnauthorizedError(user, "get workspace")
+
         return workspace
 
     @classmethod
diff --git a/atst/models/workspace.py b/atst/models/workspace.py
index 151889a6..1f82a594 100644
--- a/atst/models/workspace.py
+++ b/atst/models/workspace.py
@@ -19,3 +19,7 @@ class Workspace(Base, TimestampsMixin):
     @property
     def owner(self):
         return self.request.creator
+
+    @property
+    def users(self):
+        return set(role.user for role in self.roles)
diff --git a/tests/domain/test_workspaces.py b/tests/domain/test_workspaces.py
index 29dc231e..abdd2cca 100644
--- a/tests/domain/test_workspaces.py
+++ b/tests/domain/test_workspaces.py
@@ -1,9 +1,8 @@
 import pytest
 from uuid import uuid4
 
-from atst.domain.exceptions import NotFoundError
+from atst.domain.exceptions import NotFoundError, UnauthorizedError
 from atst.domain.workspaces import Workspaces
-from atst.domain.workspace_users import WorkspaceUsers
 
 from tests.factories import WorkspaceFactory, RequestFactory, UserFactory
 
@@ -21,15 +20,9 @@ def test_default_workspace_name_is_request_id():
     assert workspace.name == str(request.id)
 
 
-def test_can_get_workspace():
-    workspace = WorkspaceFactory.create()
-    found = Workspaces.get(workspace.id)
-    assert workspace == found
-
-
-def test_nonexistent_workspace_raises():
+def test_get_nonexistent_workspace_raises():
     with pytest.raises(NotFoundError):
-        Workspaces.get(uuid4())
+        Workspaces.get(UserFactory.build(), uuid4())
 
 
 def test_can_get_workspace_by_request():
@@ -42,8 +35,7 @@ def test_creating_workspace_adds_owner():
     user = UserFactory.create()
     request = RequestFactory.create(creator=user)
     workspace = Workspaces.create(request)
-    workspace_user = WorkspaceUsers.get(workspace.id, user.id)
-    assert workspace_user.workspace_role
+    assert workspace.roles[0].user == user
 
 
 def test_workspace_has_timestamps():
@@ -52,7 +44,13 @@ def test_workspace_has_timestamps():
     assert workspace.time_created == workspace.time_updated
 
 
-def test_workspace_has_roles():
-    request = RequestFactory.create()
-    workspace = Workspaces.create(request)
-    assert workspace.roles[0].user == request.creator
+def test_workspaces_get_ensures_user_is_in_workspace():
+    owner = UserFactory.create()
+    outside_user = UserFactory.create()
+    workspace = Workspaces.create(RequestFactory.create(creator=owner))
+
+    workspace_ = Workspaces.get(owner, workspace.id)
+    assert workspace_ == workspace
+
+    with pytest.raises(UnauthorizedError):
+        Workspaces.get(outside_user, workspace.id)