diff --git a/config/schema/yamlform.schema.yml b/config/schema/yamlform.schema.yml
index 884e820..34b570c 100644
--- a/config/schema/yamlform.schema.yml
+++ b/config/schema/yamlform.schema.yml
@@ -253,6 +253,9 @@ yamlform.yamlform.*:
         form_submit_label:
           type: label
           label: 'Form submit text'
+        form_submit_classes:
+          type: string
+          label: 'Form submit CSS classes'
         form_closed_message:
           type: text
           label: 'Form closed message'
diff --git a/src/Entity/YamlForm.php b/src/Entity/YamlForm.php
index c54a7aa..4da9292 100644
--- a/src/Entity/YamlForm.php
+++ b/src/Entity/YamlForm.php
@@ -437,6 +437,7 @@ class YamlForm extends ConfigEntityBundleBase implements YamlFormInterface {
       'page_submit_path' => '',
       'page_confirm_path' => '',
       'form_submit_label' => '',
+      'form_submit_classes' => '',
       'form_exception_message' => '',
       'form_closed_message' => '',
       'form_confidential' => FALSE,
diff --git a/src/YamlFormEntitySettingsForm.php b/src/YamlFormEntitySettingsForm.php
index 816e8ee..118817f 100644
--- a/src/YamlFormEntitySettingsForm.php
+++ b/src/YamlFormEntitySettingsForm.php
@@ -178,6 +178,11 @@ class YamlFormEntitySettingsForm extends EntityForm {
       '#size' => 20,
       '#default_value' => $settings['form_submit_label'],
     ];
+    $form['form']['form_submit_classes'] = [
+      '#type' => 'textfield',
+      '#title' => $this->t('Form submit button CSS classes'),
+      '#default_value' => $settings['form_submit_classes'],
+    ];
     $form['form']['form_prepopulate'] = [
       '#type' => 'checkbox',
       '#title' => $this->t('Allow elements to be populated using query string parameters.'),
diff --git a/src/YamlFormSubmissionForm.php b/src/YamlFormSubmissionForm.php
index 02716f4..35882d7 100644
--- a/src/YamlFormSubmissionForm.php
+++ b/src/YamlFormSubmissionForm.php
@@ -451,9 +451,15 @@ class YamlFormSubmissionForm extends ContentEntityForm {
     // Mark the submit action as the primary action, when it appears.
     $element['submit']['#button_type'] = 'primary';
 
-    // Customize the submit button's label for new submissions only.
+    // Customize the submit button's label and CSS classes for new submissions only.
     if ($yamlform_submission->isNew() || $yamlform_submission->isDraft()) {
       $element['submit']['#value'] = $this->getYamlFormSetting('form_submit_label');
+      // Create attributes' css class array if doesn't exist.
+      if (!isset($element['submit']['#attributes']['class'])) {
+        $element['submit']['#attributes']['class'] = array();
+      }
+      // Merge custom classes into attributes' class array.
+      $element['submit']['#attributes']['class'] = array_merge($element['submit']['#attributes']['class'], explode(' ', $this->getYamlFormSetting('form_submit_classes')));
     }
 
     // Add validate and complete handler to submit.