diff --git a/src/Element/InlineEntityForm.php b/src/Element/InlineEntityForm.php
index 7de4012..04b8086 100644
--- a/src/Element/InlineEntityForm.php
+++ b/src/Element/InlineEntityForm.php
@@ -8,6 +8,7 @@ use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\Render\Element\RenderElement;
 use Drupal\inline_entity_form\ElementSubmit;
 use Drupal\inline_entity_form\TranslationHelper;
+use Drupal\inline_entity_form\WidgetSubmit;
 
 /**
  * Provides an inline entity form element.
@@ -147,10 +148,17 @@ class InlineEntityForm extends RenderElement {
 
     $inline_form_handler = static::getInlineFormHandler($entity_form['#entity_type']);
     $entity_form = $inline_form_handler->entityForm($entity_form, $form_state);
+
     // The form element can't rely on inline_entity_form_form_alter() calling
     // ElementSubmit::attach() since form alters run before #process callbacks.
     ElementSubmit::attach($complete_form, $form_state);
 
+    if (isset($complete_form['settings']['block_form'])) {
+      // Attach the WidgetSubmit handler to inline blocks submitted
+      // by Layout builder.
+      WidgetSubmit::attach($complete_form['settings']['block_form'], $form_state);
+    }
+
     return $entity_form;
   }
 
diff --git a/src/WidgetSubmit.php b/src/WidgetSubmit.php
index 98921a4..ff2bf43 100644
--- a/src/WidgetSubmit.php
+++ b/src/WidgetSubmit.php
@@ -22,11 +22,16 @@ class WidgetSubmit {
    * @param \Drupal\Core\Form\FormStateInterface $form_state
    *   The form state.
    */
-  public static function attach(&$form, FormStateInterface $form_state) {
+  public static function attach(array &$form, FormStateInterface $form_state) {
     // $form['#ief_element_submit'] runs after the #ief_element_submit
     // callbacks of all subelements, which means that doSubmit() has
     // access to the final IEF $form_state.
+    if (isset($form['#ief_widget_submit_attached'])) {
+      return;
+    }
+
     $form['#ief_element_submit'][] = [get_called_class(), 'doSubmit'];
+    $form['#ief_widget_submit_attached'] = TRUE;
   }
 
   /**