diff --git a/admin/tool/uploaduser/classes/process.php b/admin/tool/uploaduser/classes/process.php
index c3820a4fa12..f817797bb52 100644
--- a/admin/tool/uploaduser/classes/process.php
+++ b/admin/tool/uploaduser/classes/process.php
@@ -688,6 +688,17 @@ class process {
                 break;
 
             case UU_USER_ADD_UPDATE:
+                if ($this->get_match_on_email()) {
+                    if ($usersbyname = $DB->get_records('user', ['username' => $user->username])) {
+                        foreach ($usersbyname as $userbyname) {
+                            if (strtolower($userbyname->email) != strtolower($user->email)) {
+                                $this->usersskipped++;
+                                $this->upt->track('status', get_string('usernotaddedusernameexists', 'error'), 'warning');
+                                $skip = true;
+                            }
+                        }
+                    }
+                }
                 break;
 
             case UU_USER_UPDATE:
diff --git a/admin/tool/uploaduser/tests/behat/upload_users.feature b/admin/tool/uploaduser/tests/behat/upload_users.feature
index 18b00b8f6c8..11a38cdfc68 100644
--- a/admin/tool/uploaduser/tests/behat/upload_users.feature
+++ b/admin/tool/uploaduser/tests/behat/upload_users.feature
@@ -296,3 +296,25 @@ Feature: Upload users
     And I navigate to "Users > Accounts > Browse list of users" in site administration
     And I should see "Bilbo Baggins"
     And I should not see "Frodo Baggins"
+
+  @javascript
+  Scenario: Create a new user when matching them on email where where the username already exists
+    Given the following "users" exist:
+      | username | firstname | lastname | email               |
+      | bilbob   | Samwise   | Gamgee   | samwise@example.com |
+      | frodob   | Frodeo    | Baspins  | frodo@example.com   |
+    And I log in as "admin"
+    And I navigate to "Users > Accounts > Upload users" in site administration
+    When I upload "lib/tests/fixtures/upload_users_email_matching.csv" file to "File" filemanager
+    And I press "Upload users"
+    Then I should see "Upload users preview"
+    And I set the following fields to these values:
+      | Upload type            | Add new and update existing users |
+      | Existing user details  | Override with file                |
+      | Match on email address | Yes                               |
+    And I press "Upload users"
+    And I should see "User not added - username already exists under a different email"
+    And I press "Continue"
+    And I navigate to "Users > Accounts > Browse list of users" in site administration
+    And I should see "Samwise Gamgee"
+    And I should see "Frodo Baggins"
diff --git a/lang/en/error.php b/lang/en/error.php
index 135cf7d648c..f1df8d9da2b 100644
--- a/lang/en/error.php
+++ b/lang/en/error.php
@@ -614,6 +614,7 @@ $string['usermustbemnet'] = 'Users in the MNET access control list must be remot
 $string['usernamelowercase'] = 'The username must be in lower case';
 $string['usernotaddederror'] = 'User not added - error';
 $string['usernotaddedregistered'] = 'User not added - already registered';
+$string['usernotaddedusernameexists'] = 'User not added - username already exists under a different email';
 $string['usernotavailable'] = 'The details of this user are not available to you';
 $string['usernotdeletedadmin'] = 'User not deleted as administrator accounts cannot be deleted.';
 $string['usernotdeleteddeleted'] = 'This user has already been deleted.';