diff --git a/packages/block-library/src/post-comments-form/index.php b/packages/block-library/src/post-comments-form/index.php
index 94278333bc107c..0d61951c122460 100644
--- a/packages/block-library/src/post-comments-form/index.php
+++ b/packages/block-library/src/post-comments-form/index.php
@@ -46,3 +46,18 @@ function register_block_core_post_comments_form() {
 	);
 }
 add_action( 'init', 'register_block_core_post_comments_form' );
+
+/**
+ * Use the button block classes for the form-submit button.
+ *
+ * @param array $fields The default comment form arguments.
+ *
+ * @return array Returns the modified fields.
+ */
+function gutenberg_comment_form_block_form_defaults( $fields ) {
+	$fields['submit_button'] = '<input name="%1$s" type="submit" id="%2$s" class="%3$s wp-block-button__link" value="%4$s" />';
+	$fields['submit_field']  = '<p class="form-submit wp-block-button">%1$s %2$s</p>';
+
+	return $fields;
+}
+add_filter( 'comment_form_defaults', 'gutenberg_comment_form_block_form_defaults' );
diff --git a/packages/block-library/src/post-comments-form/style.scss b/packages/block-library/src/post-comments-form/style.scss
index 68a73d8174b803..331d50f90ac731 100644
--- a/packages/block-library/src/post-comments-form/style.scss
+++ b/packages/block-library/src/post-comments-form/style.scss
@@ -1,22 +1,9 @@
 // Styles copied from button block styles.
 .wp-block-post-comments-form input[type="submit"] {
-	color: $white;
-	background-color: #32373c;
 	border: none;
-	border-radius: 9999px; // 100% causes an oval, but any explicit but really high value retains the pill shape.
 	box-shadow: none;
 	cursor: pointer;
 	display: inline-block;
-	font-size: 1.125em;
-	padding: 0.667em 1.333em;
 	text-align: center;
-	text-decoration: none;
 	overflow-wrap: break-word;
-
-	&:hover,
-	&:focus,
-	&:active,
-	&:visited {
-		color: $white;
-	}
 }