diff -u b/core/modules/ckeditor/ckeditor.admin.inc b/core/modules/ckeditor/ckeditor.admin.inc
--- b/core/modules/ckeditor/ckeditor.admin.inc
+++ b/core/modules/ckeditor/ckeditor.admin.inc
@@ -63,7 +63,7 @@
   $rtl = $language_direction === 'rtl' ? '_rtl' : '';
 
   $build_button_item = function($button, $rtl) {
-
+    global $base_url;
     // Set additional attribute on the button if it can occur multiple times.
     if (!empty($button['multiple'])) {
       $button['attributes']['class'][] = 'ckeditor-multiple-button';
@@ -82,6 +82,7 @@
     $button_item = $button + array(
       'rtl' => $rtl,
       'attributes' => new Attribute($attributes),
+      'base_url' => $base_url,
     );
     // If this button has group information, add it to the attributes.
     if (!empty($button['group'])) {
diff -u b/core/modules/ckeditor/templates/ckeditor-settings-toolbar.html.twig b/core/modules/ckeditor/templates/ckeditor-settings-toolbar.html.twig
--- b/core/modules/ckeditor/templates/ckeditor-settings-toolbar.html.twig
+++ b/core/modules/ckeditor/templates/ckeditor-settings-toolbar.html.twig
@@ -23,7 +23,7 @@
     <a href="#" role="button" title="{{ button.label }}" aria-label="{{ button.label }}">
       <span class="cke_button_icon">
         {# @todo Double check the #uri doesn't need to be converted to a url. Likely broken. #}
-        <img src="{{ button.image ~ direction == 'rtl' ? '_rtl' }}" title="{{ button.label }}">
+        <img src="{{ button.base_url ~ '/' ~ button.image }}" title="{{ button.label }}">
       </span>
     </a>
   {% else %}
@@ -48,7 +48,7 @@
           <label for="ckeditor-available-buttons">{{ 'Available buttons'|t }}</label>
           <ul id="ckeditor-available-buttons" class="ckeditor-buttons" role="form" data-drupal-ckeditor-button-sorting="source">
           {% for disabled_button in disabled_buttons %}
-             <li{{ disabled_button.attributes }}>{{ ckeditor.button(disabled_button) }} }}</li>
+             <li{{ disabled_button.attributes }}>{{ ckeditor.button(disabled_button) }}</li>
           {% endfor %}
           </ul>
         </div>