diff --git a/lib/compat/wordpress-5.9/block-template-utils.php b/lib/compat/wordpress-5.9/block-template-utils.php
index 37ae365ccc4f0b..4b693237e5cad4 100644
--- a/lib/compat/wordpress-5.9/block-template-utils.php
+++ b/lib/compat/wordpress-5.9/block-template-utils.php
@@ -36,7 +36,7 @@ function get_block_theme_folders( $theme_stylesheet = null ) {
 		$root_dir   = get_theme_root( $theme_name );
 		$theme_dir  = "$root_dir/$theme_name";
 
-		if ( is_readable( $theme_dir . '/block-templates/index.html' ) ) {
+		if ( file_exists( $theme_dir . '/block-templates' ) || file_exists( $theme_dir . '/block-template-parts' ) ) {
 			return array(
 				'wp_template'      => 'block-templates',
 				'wp_template_part' => 'block-template-parts',
diff --git a/packages/block-library/src/template-part/index.php b/packages/block-library/src/template-part/index.php
index 1eb8e39d780e39..20bc6900f83bb0 100644
--- a/packages/block-library/src/template-part/index.php
+++ b/packages/block-library/src/template-part/index.php
@@ -64,8 +64,11 @@ function render_block_core_template_part( $attributes ) {
 		} else {
 			// Else, if the template part was provided by the active theme,
 			// render the corresponding file content.
-			$theme_folders           = get_block_theme_folders();
-			$template_part_file_path = get_theme_file_path( '/' . $theme_folders['wp_template_part'] . '/' . $attributes['slug'] . '.html' );
+			$parent_theme_folders        = get_block_theme_folders( get_template() );
+			$child_theme_folders         = get_block_theme_folders( get_stylesheet() );
+			$child_theme_part_file_path  = get_theme_file_path( '/' . $child_theme_folders['wp_template_part'] . '/' . $attributes['slug'] . '.html' );
+			$parent_theme_part_file_path = get_theme_file_path( '/' . $parent_theme_folders['wp_template_part'] . '/' . $attributes['slug'] . '.html' );
+			$template_part_file_path     = 0 === validate_file( $attributes['slug'] ) && file_exists( $child_theme_part_file_path ) ? $child_theme_part_file_path : $parent_theme_part_file_path;
 			if ( 0 === validate_file( $attributes['slug'] ) && file_exists( $template_part_file_path ) ) {
 				$content = file_get_contents( $template_part_file_path );
 				$content = is_string( $content ) && '' !== $content