diff --git a/packages/block-library/src/post-comments-form/form.js b/packages/block-library/src/post-comments-form/form.js
index 51212c925cec5..d9c11d0be80e0 100644
--- a/packages/block-library/src/post-comments-form/form.js
+++ b/packages/block-library/src/post-comments-form/form.js
@@ -1,7 +1,13 @@
+/**
+ * External dependencies
+ */
+import classnames from 'classnames';
+
 /**
  * WordPress dependencies
  */
 import { __ } from '@wordpress/i18n';
+import { __experimentalElementButtonClassName } from '@wordpress/block-editor';
 import { useDisabled, useInstanceId } from '@wordpress/compose';
 
 const CommentsForm = () => {
@@ -27,7 +33,11 @@ const CommentsForm = () => {
 					<input
 						name="submit"
 						type="submit"
-						className="submit wp-block-button__link"
+						className={ classnames(
+							'submit',
+							'wp-block-button__link',
+							__experimentalElementButtonClassName
+						) }
 						label={ __( 'Post Comment' ) }
 						value={ __( 'Post Comment' ) }
 					/>
diff --git a/packages/block-library/src/post-comments-form/index.php b/packages/block-library/src/post-comments-form/index.php
index accceace3cdb9..c2ef5bcb762a6 100644
--- a/packages/block-library/src/post-comments-form/index.php
+++ b/packages/block-library/src/post-comments-form/index.php
@@ -72,7 +72,7 @@ function register_block_core_post_comments_form() {
  */
 function post_comments_form_block_form_defaults( $fields ) {
 	if ( wp_is_block_theme() ) {
-		$fields['submit_button'] = '<input name="%1$s" type="submit" id="%2$s" class="%3$s wp-block-button__link" value="%4$s" />';
+		$fields['submit_button'] = '<input name="%1$s" type="submit" id="%2$s" class="%3$s wp-block-button__link ' . WP_Theme_JSON_Gutenberg::__EXPERIMENTAL_ELEMENT_BUTTON_CLASS_NAME . '" value="%4$s" />';
 		$fields['submit_field']  = '<p class="form-submit wp-block-button">%1$s %2$s</p>';
 	}
 
diff --git a/packages/block-library/src/post-comments/index.php b/packages/block-library/src/post-comments/index.php
index 2b20a9494eef3..5520184408b24 100644
--- a/packages/block-library/src/post-comments/index.php
+++ b/packages/block-library/src/post-comments/index.php
@@ -78,7 +78,7 @@ function register_block_core_post_comments() {
  */
 function post_comments_block_form_defaults( $fields ) {
 	if ( wp_is_block_theme() ) {
-		$fields['submit_button'] = '<input name="%1$s" type="submit" id="%2$s" class="%3$s wp-block-button__link" value="%4$s" />';
+		$fields['submit_button'] = '<input name="%1$s" type="submit" id="%2$s" class="%3$s wp-block-button__link ' . WP_Theme_JSON_Gutenberg::__EXPERIMENTAL_ELEMENT_BUTTON_CLASS_NAME . '" value="%4$s" />';
 		$fields['submit_field']  = '<p class="form-submit wp-block-button">%1$s %2$s</p>';
 	}