diff --git a/assets/js/actions/guest.js b/assets/js/actions/guest.js
index 2e50efcac..a26317d47 100644
--- a/assets/js/actions/guest.js
+++ b/assets/js/actions/guest.js
@@ -4,9 +4,10 @@ export const SET_CODE = "SET_CODE"
 export const GENERATE_CODE = "GENERATE_CODE"
 export const CLEAR = "CLEAR"
 
-export const changeEmail = (email) => ({
+export const changeEmail = (email, collaborators = []) => ({
   type: CHANGE_EMAIL,
   email,
+  collaborators,
 })
 
 export const changeLevel = (level) => ({
diff --git a/assets/js/components/collaborators/CollaboratorIndex.jsx b/assets/js/components/collaborators/CollaboratorIndex.jsx
index 9dcfb5bfe..4ffa7d6af 100644
--- a/assets/js/components/collaborators/CollaboratorIndex.jsx
+++ b/assets/js/components/collaborators/CollaboratorIndex.jsx
@@ -24,16 +24,6 @@ class CollaboratorIndex extends Component {
     $("#addCollaborator").modal("open")
   }
 
-  loadCollaboratorToEdit(event, collaborator) {
-    event.preventDefault()
-    if (collaborator.invited) {
-      this.props.guestActions.changeEmail(collaborator.email)
-      this.props.guestActions.changeLevel(collaborator.role)
-      this.props.guestActions.setCode(collaborator.code)
-      $("#addCollaborator").modal("open")
-    }
-  }
-
   levelChanged(e, collaborator) {
     const { projectId, inviteActions, actions, t } = this.props
     const level = e.target.value
@@ -143,9 +133,8 @@ class CollaboratorIndex extends Component {
           modalId="addCollaborator"
           modalText={t("The access of project collaborators will be managed through roles")}
           header={t("Invite collaborators")}
-          confirmationText={t("Accept")}
-          onConfirm={(event) => event.preventDefault()}
           style={{ maxWidth: "800px" }}
+          collaborators={collaborators}
         />
         <div>
           <CardTable title={title}>
diff --git a/assets/js/components/collaborators/InviteModal.jsx b/assets/js/components/collaborators/InviteModal.jsx
index 8ee7d2d4b..fe2eed667 100644
--- a/assets/js/components/collaborators/InviteModal.jsx
+++ b/assets/js/components/collaborators/InviteModal.jsx
@@ -32,7 +32,7 @@ export class InviteModal extends Component {
   }
 
   emailOnChange(e) {
-    this.props.guestActions.changeEmail(e.target.value)
+    this.props.guestActions.changeEmail(e.target.value, this.props.collaborators)
   }
 
   emailOnBlur(e) {
@@ -42,7 +42,7 @@ export class InviteModal extends Component {
       return
     }
     if (newEmail != config.user) {
-      Promise.resolve(this.props.guestActions.changeEmail(newEmail)).then(() => {
+      Promise.resolve(this.props.guestActions.changeEmail(newEmail, this.props.collaborators)).then(() => {
         Promise.resolve(
           this.props.actions.getInviteByEmailAndProject(projectId, guest.data.email)
         ).then((dbGuest) => {
@@ -97,10 +97,10 @@ export class InviteModal extends Component {
       </a>
     )
 
-    const validEmail = guest.data.email && !guest.errors.email
+    const emailError = this.getEmailError(guest);
 
     const sendButton =
-      guest.data.code && validEmail ? (
+      guest.data.code && !emailError ? (
         <a
           href="#!"
           className=" modal-action modal-close waves-effect btn-medium blue"
@@ -150,9 +150,9 @@ export class InviteModal extends Component {
                       }}
                     />
                   </InputWithLabel>
-                  {!validEmail ? (
+                  {emailError ? (
                     <span className="small-text-bellow text-error">
-                      {t("Please enter a valid email")}
+                      {t(emailError)}
                     </span>
                   ) : (
                     <span />
@@ -189,6 +189,23 @@ export class InviteModal extends Component {
       </Modal>
     )
   }
+
+  getEmailError(guest) {
+    let errorCode = "invalid-email";
+    if (guest.data.email) {
+      errorCode = guest.errors.email
+    }
+
+    switch (errorCode) {
+      case null:
+        return null;
+      case "existing-email":
+        return "Email already in project";
+      case "invalid-email":
+      default:
+        return "Please enter a valid email";
+    }
+  }
 }
 
 InviteModal.propTypes = {
@@ -202,12 +219,11 @@ InviteModal.propTypes = {
   linkText: PropTypes.string,
   header: PropTypes.string.isRequired,
   modalText: PropTypes.string.isRequired,
-  confirmationText: PropTypes.string.isRequired,
-  onConfirm: PropTypes.func.isRequired,
   modalId: PropTypes.string.isRequired,
   projectId: PropTypes.number,
   style: PropTypes.object,
   userLevel: PropTypes.string,
+  collaborators: PropTypes.array,
 }
 
 const mapDispatchToProps = (dispatch) => ({
@@ -220,6 +236,7 @@ const mapStateToProps = (state) => ({
   projectId: state.project.data.id,
   userLevel: state.project.data.level,
   guest: state.guest,
+  collaborators: state.collaborators.items,
 })
 
 export default translate()(connect(mapStateToProps, mapDispatchToProps)(InviteModal))
diff --git a/assets/js/reducers/guest.js b/assets/js/reducers/guest.js
index 718f5f563..e4eef8a04 100644
--- a/assets/js/reducers/guest.js
+++ b/assets/js/reducers/guest.js
@@ -34,6 +34,16 @@ const validEmail = (email) => {
 }
 
 const changeEmail = (state, action) => {
+  const { email, collaborators } = action;
+  let emailError = null;
+  if (!validEmail(email)) {
+    emailError = "invalid-email";
+  } else {
+    const collaborator = collaborators.find((c) => c.email === email);
+    if (collaborator) {
+      emailError = "existing-email";
+    }
+  }
   return {
     ...state,
     data: {
@@ -41,8 +51,8 @@ const changeEmail = (state, action) => {
       email: action.email,
     },
     errors: {
-      ...state.errors,
-      email: !validEmail(action.email),
+      ...state.errors,  
+      email: emailError,
     },
   }
 }
diff --git a/test/ask_web/controllers/invite_controller_test.exs b/test/ask_web/controllers/invite_controller_test.exs
index 863bd10a6..9b450bef1 100644
--- a/test/ask_web/controllers/invite_controller_test.exs
+++ b/test/ask_web/controllers/invite_controller_test.exs
@@ -1095,7 +1095,7 @@ defmodule AskWeb.InviteControllerTest do
   end
 
   test "send invite to existing user", %{conn: conn, user: user} do
-    Process.register self(), :mail_target
+    Process.register(self(), :mail_target)
     project = create_project_for_user(user)
     code = "ABC1234"
     level = "reader"