diff --git a/templates/admin/update_manager/index.html.twig b/templates/admin/update_manager/index.html.twig
index eb8c7548..d9dccbcf 100644
--- a/templates/admin/update_manager/index.html.twig
+++ b/templates/admin/update_manager/index.html.twig
@@ -133,7 +133,7 @@
                         </div>
 
                         {% if status.update_available and status.can_auto_update and validation.valid %}
-                            <form action="{{ path('admin_update_manager_start') }}" method="post" onsubmit="return confirm('{% trans %}update_manager.confirm_update{% endtrans %}');">
+                            <form action="{{ path('admin_update_manager_start') }}" method="post" onsubmit="return confirmVersionChange('{{ status.latest_tag }}', false);">
                                 <input type="hidden" name="_token" value="{{ csrf_token('update_manager_start') }}">
                                 <input type="hidden" name="version" value="{{ status.latest_tag }}">
 
@@ -237,7 +237,7 @@
                                                 </a>
                                                 {% if release.version != status.current_version and status.can_auto_update and validation.valid %}
                                                     <form action="{{ path('admin_update_manager_start') }}" method="post" class="d-inline"
-                                                          onsubmit="return confirm('{% if release.version > status.current_version %}{% trans %}update_manager.confirm_update{% endtrans %}{% else %}{% trans %}update_manager.confirm_downgrade{% endtrans %}{% endif %}');">
+                                                          onsubmit="return confirmVersionChange('{{ release.tag }}', {{ release.version < status.current_version ? 'true' : 'false' }});">
                                                         <input type="hidden" name="_token" value="{{ csrf_token('update_manager_start') }}">
                                                         <input type="hidden" name="version" value="{{ release.tag }}">
                                                         <input type="hidden" name="backup" value="1">
@@ -371,4 +371,37 @@
         </div>
     {% endif %}
 </div>
+
+<script>
+// Version where Update Manager was introduced
+const UPDATE_MANAGER_MIN_VERSION = '2.6.0';
+
+function confirmVersionChange(targetVersion, isDowngrade) {
+    const targetClean = targetVersion.replace(/^v/, '');
+
+    if (isDowngrade) {
+        // Check if downgrading to a version without Update Manager
+        if (compareVersions(targetClean, UPDATE_MANAGER_MIN_VERSION) < 0) {
+            return confirm(
+                '{% trans %}update_manager.confirm_downgrade{% endtrans %}\n\n' +
+                '⚠️ {% trans %}update_manager.downgrade_removes_update_manager{% endtrans %}'
+            );
+        }
+        return confirm('{% trans %}update_manager.confirm_downgrade{% endtrans %}');
+    }
+    return confirm('{% trans %}update_manager.confirm_update{% endtrans %}');
+}
+
+function compareVersions(v1, v2) {
+    const parts1 = v1.split('.').map(Number);
+    const parts2 = v2.split('.').map(Number);
+    for (let i = 0; i < Math.max(parts1.length, parts2.length); i++) {
+        const p1 = parts1[i] || 0;
+        const p2 = parts2[i] || 0;
+        if (p1 < p2) return -1;
+        if (p1 > p2) return 1;
+    }
+    return 0;
+}
+</script>
 {% endblock %}
diff --git a/translations/messages.en.xlf b/translations/messages.en.xlf
index ff0a05e6..592590a8 100644
--- a/translations/messages.en.xlf
+++ b/translations/messages.en.xlf
@@ -14988,5 +14988,11 @@ Buerklin-API Authentication server:
         <target>Are you sure you want to downgrade Part-DB? This will revert to an older version. A backup will be created before the downgrade.</target>
       </segment>
     </unit>
+    <unit id="um_downgrade_removes_update_manager" name="update_manager.downgrade_removes_update_manager">
+      <segment state="translated">
+        <source>update_manager.downgrade_removes_update_manager</source>
+        <target>WARNING: This version does not include the Update Manager. After downgrading, you will need to update manually using the command line (git checkout, composer install, etc.).</target>
+      </segment>
+    </unit>
   </file>
 </xliff>