diff --git a/admin/tool/cohortroles/classes/api.php b/admin/tool/cohortroles/classes/api.php
index 89f54aea73d..335272c99f0 100644
--- a/admin/tool/cohortroles/classes/api.php
+++ b/admin/tool/cohortroles/classes/api.php
@@ -179,6 +179,7 @@ class api {
                            AND ra.roleid = :roleid
                            AND ra.userid = :userid
                          WHERE cm.cohortid ' . $cohortsql . '
+                           AND u.deleted = 0
                            AND ra.id IS NULL';
 
                 $toadd = $DB->get_records_sql($sql, $params);
diff --git a/admin/tool/cohortroles/classes/observers.php b/admin/tool/cohortroles/classes/observers.php
new file mode 100644
index 00000000000..4e2d6907ad0
--- /dev/null
+++ b/admin/tool/cohortroles/classes/observers.php
@@ -0,0 +1,43 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+declare(strict_types=1);
+
+namespace tool_cohortroles;
+
+use core\event\user_deleted;
+
+/**
+ * Plugin event observer callbacks
+ *
+ * @package    tool_cohortroles
+ * @copyright  2023 Paul Holden <paulh@moodle.com>
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class observers {
+
+    /**
+     * User deleted event, remove cohort role assignments specific to them
+     *
+     * @param user_deleted $event
+     */
+    public static function user_deleted(user_deleted $event): void {
+        $cohortroleassignments = cohort_role_assignment::get_records(['userid' => $event->objectid]);
+        foreach ($cohortroleassignments as $cohortroleassignment) {
+            $cohortroleassignment->delete();
+        }
+    }
+}
diff --git a/admin/tool/cohortroles/db/events.php b/admin/tool/cohortroles/db/events.php
new file mode 100644
index 00000000000..53d982aa150
--- /dev/null
+++ b/admin/tool/cohortroles/db/events.php
@@ -0,0 +1,32 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Plugin event observers
+ *
+ * @package    tool_cohortroles
+ * @copyright  2023 Paul Holden <paulh@moodle.com>
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+defined('MOODLE_INTERNAL') || die();
+
+$observers = [
+    [
+        'eventname' => '\core\event\user_deleted',
+        'callback' => '\tool_cohortroles\observers::user_deleted',
+    ],
+];
diff --git a/admin/tool/cohortroles/db/upgrade.php b/admin/tool/cohortroles/db/upgrade.php
index b08f4ca8d06..7c2e0b188d4 100644
--- a/admin/tool/cohortroles/db/upgrade.php
+++ b/admin/tool/cohortroles/db/upgrade.php
@@ -50,5 +50,13 @@ function xmldb_tool_cohortroles_upgrade($oldversion) {
     // Automatically generated Moodle v4.1.0 release upgrade line.
     // Put any upgrade step following this.
 
+    if ($oldversion < 2022112801) {
+        // Delete any tool_cohortroles mappings for users who no longer exist.
+        $DB->delete_records_select('tool_cohortroles', 'userid NOT IN (SELECT id FROM {user} WHERE deleted = 0)');
+
+        // Cohortroles savepoint reached.
+        upgrade_plugin_savepoint(true, 2022112801, 'tool', 'cohortroles');
+    }
+
     return true;
 }
diff --git a/admin/tool/cohortroles/version.php b/admin/tool/cohortroles/version.php
index fcc1c5bf77b..68d041d8832 100644
--- a/admin/tool/cohortroles/version.php
+++ b/admin/tool/cohortroles/version.php
@@ -24,8 +24,7 @@
 
 defined('MOODLE_INTERNAL') || die();
 
-
-$plugin->version   = 2022112800; // The current plugin version (Date: YYYYMMDDXX).
+$plugin->version   = 2022112801; // The current plugin version (Date: YYYYMMDDXX).
 $plugin->requires  = 2022111800; // Requires this Moodle version.
 $plugin->component = 'tool_cohortroles'; // Full name of the plugin (used for diagnostics).