diff --git a/client/modules/User/pages/SignupView.jsx b/client/modules/User/pages/SignupView.jsx
index 13ee2909..9fbbc930 100644
--- a/client/modules/User/pages/SignupView.jsx
+++ b/client/modules/User/pages/SignupView.jsx
@@ -59,10 +59,26 @@ class SignupView extends React.Component {
   }
 }
 
+function asyncErrorsSelector(formName, state) {
+  const form = state.form[formName];
+  if (!form) {
+    return {};
+  }
+
+  const fieldNames = Object.keys(form).filter(key => !key.startsWith('_'));
+  return fieldNames.reduce((asyncErrors, fieldName) => {
+    if (form[fieldName].asyncError) {
+      return { ...asyncErrors, [fieldName]: form[fieldName].asyncError };
+    }
+    return asyncErrors;
+  }, {});
+}
+
 function mapStateToProps(state) {
   return {
     user: state.user,
-    previousPath: state.ide.previousPath
+    previousPath: state.ide.previousPath,
+    asyncErrors: asyncErrorsSelector('signup', state)
   };
 }
 
@@ -71,21 +87,29 @@ function mapDispatchToProps(dispatch) {
 }
 
 function asyncValidate(formProps, dispatch, props) {
-  const fieldToValidate = props.form._active;
-  if (fieldToValidate) {
-    const queryParams = {};
-    queryParams[fieldToValidate] = formProps[fieldToValidate];
-    queryParams.check_type = fieldToValidate;
-    return axios.get('/api/signup/duplicate_check', { params: queryParams })
-      .then((response) => {
-        if (response.data.exists) {
-          const error = {};
-          error[fieldToValidate] = response.data.message;
-          throw error;
-        }
-      });
-  }
-  return Promise.resolve(true).then(() => {});
+  const errors = {};
+  return Promise.resolve(true)
+    .then(() => {
+      const fieldToValidate = props.form._active;
+      if (fieldToValidate) {
+        const queryParams = {};
+        queryParams[fieldToValidate] = formProps[fieldToValidate];
+        queryParams.check_type = fieldToValidate;
+        return axios.get('/api/signup/duplicate_check', { params: queryParams })
+          .then((response) => {
+            if (response.data.exists) {
+              errors[fieldToValidate] = response.data.message;
+            }
+          });
+      }
+      return null;
+    })
+    .then(() => {
+      const err = { ...errors, ...props.asyncErrors };
+      if (Object.keys(err).length > 0) {
+        throw err;
+      }
+    });
 }
 
 function onSubmitFail(errors) {
diff --git a/client/styles/components/_forms.scss b/client/styles/components/_forms.scss
index ea839663..213c3d3f 100644
--- a/client/styles/components/_forms.scss
+++ b/client/styles/components/_forms.scss
@@ -45,3 +45,7 @@
 .form input[type="submit"] {
   @extend %forms-button;
 }
+
+.form input[type="submit"]:disabled {
+  cursor: not-allowed;
+}
diff --git a/server/controllers/user.controller.js b/server/controllers/user.controller.js
index 3021d5c5..662baae3 100644
--- a/server/controllers/user.controller.js
+++ b/server/controllers/user.controller.js
@@ -38,7 +38,12 @@ export function createUser(req, res, next) {
     });
 
     User.findOne(
-      { email: req.body.email },
+      {
+        $or: [
+          { email: req.body.email },
+          { username: req.body.username }
+        ]
+      },
       (err, existingUser) => {
         if (err) {
           res.status(404).send({ error: err });
@@ -46,7 +51,8 @@ export function createUser(req, res, next) {
         }
 
         if (existingUser) {
-          res.status(422).send({ error: 'Email is in use' });
+          const fieldInUse = existingUser.email === req.body.email ? 'Email' : 'Username';
+          res.status(422).send({ error: `${fieldInUse} is in use` });
           return;
         }
         user.save((saveErr) => {