diff --git a/src/wp-includes/class-wp-theme-json.php b/src/wp-includes/class-wp-theme-json.php
index a893dfb6a9..6fd954705e 100644
--- a/src/wp-includes/class-wp-theme-json.php
+++ b/src/wp-includes/class-wp-theme-json.php
@@ -1032,7 +1032,7 @@ class WP_Theme_JSON {
 			if ( ! empty( $block_type->styles ) ) {
 				$style_selectors = array();
 				foreach ( $block_type->styles as $style ) {
-					$style_selectors[ $style['name'] ] = static::append_to_selector( '.is-style-' . $style['name'], static::$blocks_metadata[ $block_name ]['selector'] );
+					$style_selectors[ $style['name'] ] = static::get_block_style_variation_selector( $style['name'], static::$blocks_metadata[ $block_name ]['selector'] );
 				}
 				static::$blocks_metadata[ $block_name ]['styleVariations'] = $style_selectors;
 			}
@@ -3925,4 +3925,38 @@ class WP_Theme_JSON {
 		$theme_json->theme_json['styles'] = self::convert_variables_to_value( $styles, $vars );
 		return $theme_json;
 	}
+
+	/**
+	 * Generates a selector for a block style variation.
+	 *
+	 * @since 6.5.0
+	 *
+	 * @param string $variation_name Name of the block style variation.
+	 * @param string $block_selector CSS selector for the block.
+	 * @return string Block selector with block style variation selector added to it.
+	 */
+	protected static function get_block_style_variation_selector( $variation_name, $block_selector ) {
+		$variation_class = ".is-style-$variation_name";
+
+		if ( ! $block_selector ) {
+			return $variation_class;
+		}
+
+		$limit          = 1;
+		$selector_parts = explode( ',', $block_selector );
+		$result         = array();
+
+		foreach ( $selector_parts as $part ) {
+			$result[] = preg_replace_callback(
+				'/((?::\([^)]+\))?\s*)([^\s:]+)/',
+				function ( $matches ) use ( $variation_class ) {
+					return $matches[1] . $matches[2] . $variation_class;
+				},
+				$part,
+				$limit
+			);
+		}
+
+		return implode( ',', $result );
+	}
 }
diff --git a/tests/phpunit/tests/theme/wpThemeJson.php b/tests/phpunit/tests/theme/wpThemeJson.php
index ff98a98e0a..25c1d58a62 100644
--- a/tests/phpunit/tests/theme/wpThemeJson.php
+++ b/tests/phpunit/tests/theme/wpThemeJson.php
@@ -5120,4 +5120,92 @@ class Tests_Theme_wpThemeJson extends WP_UnitTestCase {
 		$sanitized_theme_json = $theme_json->get_raw_data();
 		$this->assertSameSetsWithIndex( $expected_sanitized, $sanitized_theme_json, 'Sanitized theme.json does not match' );
 	}
+
+	/**
+	 * Tests the correct application of a block style variation's selector to
+	 * a block's selector.
+	 *
+	 * @ticket 60453
+	 *
+	 * @dataProvider data_get_block_style_variation_selector
+	 *
+	 * @param string $selector  CSS selector.
+	 * @param string $expected  Expected block style variation CSS selector.
+	 */
+	public function test_get_block_style_variation_selector( $selector, $expected ) {
+		$theme_json = new ReflectionClass( 'WP_Theme_JSON' );
+
+		$func = $theme_json->getMethod( 'get_block_style_variation_selector' );
+		$func->setAccessible( true );
+
+		$actual = $func->invoke( null, 'custom', $selector );
+
+		$this->assertEquals( $expected, $actual );
+	}
+
+	/**
+	 * Data provider for generating block style variation selectors.
+	 *
+	 * @return array[]
+	 */
+	public function data_get_block_style_variation_selector() {
+		return array(
+			'empty block selector'     => array(
+				'selector' => '',
+				'expected' => '.is-style-custom',
+			),
+			'class selector'           => array(
+				'selector' => '.wp-block',
+				'expected' => '.wp-block.is-style-custom',
+			),
+			'id selector'              => array(
+				'selector' => '#wp-block',
+				'expected' => '#wp-block.is-style-custom',
+			),
+			'element tag selector'     => array(
+				'selector' => 'p',
+				'expected' => 'p.is-style-custom',
+			),
+			'attribute selector'       => array(
+				'selector' => '[style*="color"]',
+				'expected' => '[style*="color"].is-style-custom',
+			),
+			'descendant selector'      => array(
+				'selector' => '.wp-block .inner',
+				'expected' => '.wp-block.is-style-custom .inner',
+			),
+			'comma separated selector' => array(
+				'selector' => '.wp-block .inner, .wp-block .alternative',
+				'expected' => '.wp-block.is-style-custom .inner, .wp-block.is-style-custom .alternative',
+			),
+			'pseudo selector'          => array(
+				'selector' => 'div:first-child',
+				'expected' => 'div.is-style-custom:first-child',
+			),
+			':is selector'             => array(
+				'selector' => '.wp-block:is(.outer .inner:first-child)',
+				'expected' => '.wp-block.is-style-custom:is(.outer .inner:first-child)',
+			),
+			':not selector'            => array(
+				'selector' => '.wp-block:not(.outer .inner:first-child)',
+				'expected' => '.wp-block.is-style-custom:not(.outer .inner:first-child)',
+			),
+			':has selector'            => array(
+				'selector' => '.wp-block:has(.outer .inner:first-child)',
+				'expected' => '.wp-block.is-style-custom:has(.outer .inner:first-child)',
+			),
+			':where selector'          => array(
+				'selector' => '.wp-block:where(.outer .inner:first-child)',
+				'expected' => '.wp-block.is-style-custom:where(.outer .inner:first-child)',
+			),
+			'wrapping :where selector' => array(
+				'selector' => ':where(.outer .inner:first-child)',
+				'expected' => ':where(.outer.is-style-custom .inner:first-child)',
+			),
+			'complex'                  => array(
+				'selector' => '.wp:where(.something):is(.test:not(.nothing p)):has(div[style]) .content, .wp:where(.nothing):not(.test:is(.something div)):has(span[style]) .inner',
+				'expected' => '.wp.is-style-custom:where(.something):is(.test:not(.nothing p)):has(div[style]) .content, .wp.is-style-custom:where(.nothing):not(.test:is(.something div)):has(span[style]) .inner',
+			),
+		);
+	}
 }