diff --git a/src/wp-includes/block-template-utils.php b/src/wp-includes/block-template-utils.php
index 9b248c1453..6475ac36f2 100644
--- a/src/wp-includes/block-template-utils.php
+++ b/src/wp-includes/block-template-utils.php
@@ -20,6 +20,35 @@ if ( ! defined( 'WP_TEMPLATE_PART_AREA_UNCATEGORIZED' ) ) {
 	define( 'WP_TEMPLATE_PART_AREA_UNCATEGORIZED', 'uncategorized' );
 }
 
+/**
+ * For backward compatibility reasons,
+ * block themes might be using block-templates or block-template-parts,
+ * this function ensures we fallback to these folders properly.
+ *
+ * @since 5.9.0
+ *
+ * @param string $theme_stylesheet The stylesheet. Default is to leverage the main theme root.
+ *
+ * @return array Folder names used by block themes.
+ */
+function get_block_theme_folders( $theme_stylesheet = null ) {
+	$theme_name = null === $theme_stylesheet ? get_stylesheet() : $theme_stylesheet;
+	$root_dir   = get_theme_root( $theme_name );
+	$theme_dir  = "$root_dir/$theme_name";
+
+	if ( is_readable( $theme_dir . '/block-templates/index.html' ) ) {
+		return array(
+			'wp_template'      => 'block-templates',
+			'wp_template_part' => 'block-template-parts',
+		);
+	}
+
+	return array(
+		'wp_template'      => 'templates',
+		'wp_template_part' => 'parts',
+	);
+}
+
 /**
  * Returns a filtered list of allowed area values for template parts.
  *
@@ -224,16 +253,13 @@ function _get_block_template_file( $template_type, $slug ) {
 		return null;
 	}
 
-	$template_base_paths = array(
-		'wp_template'      => 'block-templates',
-		'wp_template_part' => 'block-template-parts',
-	);
-	$themes              = array(
+	$themes = array(
 		get_stylesheet() => get_stylesheet_directory(),
 		get_template()   => get_template_directory(),
 	);
 	foreach ( $themes as $theme_slug => $theme_dir ) {
-		$file_path = $theme_dir . '/' . $template_base_paths[ $template_type ] . '/' . $slug . '.html';
+		$template_base_paths = get_block_theme_folders( $theme_slug );
+		$file_path           = $theme_dir . '/' . $template_base_paths[ $template_type ] . '/' . $slug . '.html';
 		if ( file_exists( $file_path ) ) {
 			$new_template_item = array(
 				'slug'  => $slug,
@@ -272,17 +298,13 @@ function _get_block_templates_files( $template_type ) {
 		return null;
 	}
 
-	$template_base_paths = array(
-		'wp_template'      => 'block-templates',
-		'wp_template_part' => 'block-template-parts',
-	);
-	$themes              = array(
+	$themes         = array(
 		get_stylesheet() => get_stylesheet_directory(),
 		get_template()   => get_template_directory(),
 	);
-
 	$template_files = array();
 	foreach ( $themes as $theme_slug => $theme_dir ) {
+		$template_base_paths  = get_block_theme_folders( $theme_slug );
 		$theme_template_files = _get_block_templates_paths( $theme_dir . '/' . $template_base_paths[ $template_type ] );
 		foreach ( $theme_template_files as $template_file ) {
 			$template_base_path = $template_base_paths[ $template_type ];
diff --git a/src/wp-includes/theme.php b/src/wp-includes/theme.php
index 838fe23596..9d43d1b2a2 100644
--- a/src/wp-includes/theme.php
+++ b/src/wp-includes/theme.php
@@ -4084,5 +4084,6 @@ function create_initial_theme_features() {
  * @return boolean Whether the current theme is a block-based theme or not.
  */
 function wp_is_block_template_theme() {
-	return is_readable( get_theme_file_path( '/block-templates/index.html' ) );
+	return is_readable( get_theme_file_path( '/block-templates/index.html' ) ) ||
+		is_readable( get_theme_file_path( '/templates/index.html' ) );
 }
diff --git a/tests/phpunit/data/themedir1/block-theme-child/block-templates/page-1.html b/tests/phpunit/data/themedir1/block-theme-child/templates/page-1.html
similarity index 100%
rename from tests/phpunit/data/themedir1/block-theme-child/block-templates/page-1.html
rename to tests/phpunit/data/themedir1/block-theme-child/templates/page-1.html
diff --git a/tests/phpunit/data/themedir1/block-theme/block-templates/index.html b/tests/phpunit/data/themedir1/block-theme/templates/index.html
similarity index 100%
rename from tests/phpunit/data/themedir1/block-theme/block-templates/index.html
rename to tests/phpunit/data/themedir1/block-theme/templates/index.html
diff --git a/tests/phpunit/data/themedir1/block-theme/block-templates/page-home.html b/tests/phpunit/data/themedir1/block-theme/templates/page-home.html
similarity index 100%
rename from tests/phpunit/data/themedir1/block-theme/block-templates/page-home.html
rename to tests/phpunit/data/themedir1/block-theme/templates/page-home.html
diff --git a/tests/phpunit/data/themedir1/block-theme/block-templates/page.html b/tests/phpunit/data/themedir1/block-theme/templates/page.html
similarity index 100%
rename from tests/phpunit/data/themedir1/block-theme/block-templates/page.html
rename to tests/phpunit/data/themedir1/block-theme/templates/page.html
diff --git a/tests/phpunit/tests/block-template.php b/tests/phpunit/tests/block-template.php
index e97b7be17f..29a69b15da 100644
--- a/tests/phpunit/tests/block-template.php
+++ b/tests/phpunit/tests/block-template.php
@@ -37,7 +37,7 @@ class Block_Template_Test extends WP_UnitTestCase {
 		);
 		$resolved_template_path = locate_block_template( get_stylesheet_directory() . '/page-home.php', $type, $templates );
 		$this->assertEquals( self::$template_canvas_path, $resolved_template_path );
-		$this->assertStringEqualsFile( get_stylesheet_directory() . '/block-templates/page-home.html', $_wp_current_template_content );
+		$this->assertStringEqualsFile( get_stylesheet_directory() . '/templates/page-home.html', $_wp_current_template_content );
 	}
 
 	function test_page_block_template_takes_precedence() {
@@ -50,7 +50,7 @@ class Block_Template_Test extends WP_UnitTestCase {
 		);
 		$resolved_template_path = locate_block_template( get_stylesheet_directory() . '/page.php', $type, $templates );
 		$this->assertEquals( self::$template_canvas_path, $resolved_template_path );
-		$this->assertStringEqualsFile( get_stylesheet_directory() . '/block-templates/page.html', $_wp_current_template_content );
+		$this->assertStringEqualsFile( get_stylesheet_directory() . '/templates/page.html', $_wp_current_template_content );
 	}
 
 	function test_block_template_takes_precedence_over_equally_specific_php_template() {
@@ -61,7 +61,7 @@ class Block_Template_Test extends WP_UnitTestCase {
 		);
 		$resolved_template_path = locate_block_template( get_stylesheet_directory() . '/index.php', $type, $templates );
 		$this->assertEquals( self::$template_canvas_path, $resolved_template_path );
-		$this->assertStringEqualsFile( get_stylesheet_directory() . '/block-templates/index.html', $_wp_current_template_content );
+		$this->assertStringEqualsFile( get_stylesheet_directory() . '/templates/index.html', $_wp_current_template_content );
 	}
 
 	/**
@@ -128,7 +128,7 @@ class Block_Template_Test extends WP_UnitTestCase {
 		);
 		$resolved_template_path          = locate_block_template( $parent_theme_page_template_path, $type, $templates );
 		$this->assertEquals( self::$template_canvas_path, $resolved_template_path );
-		$this->assertStringEqualsFile( get_stylesheet_directory() . '/block-templates/page-1.html', $_wp_current_template_content );
+		$this->assertStringEqualsFile( get_stylesheet_directory() . '/templates/page-1.html', $_wp_current_template_content );
 	}
 
 	/**