diff --git a/rhodecode/templates/admin/users/user_edit.html b/rhodecode/templates/admin/users/user_edit.html
--- a/rhodecode/templates/admin/users/user_edit.html
+++ b/rhodecode/templates/admin/users/user_edit.html
@@ -50,7 +50,11 @@
                     <label for="username">${_('Username')}:</label>
                 </div>
                 <div class="input">
-                    ${h.text('username',class_='medium')}
+                    %if c.ldap_dn:
+                        ${h.text('username',class_='medium disabled', readonly="readonly")}
+                    %else:
+                        ${h.text('username',class_='medium')}
+                    %endif:
                 </div>
              </div>