diff --git a/src/wp-includes/class-wp-theme-json.php b/src/wp-includes/class-wp-theme-json.php
index 05f5e7b9e7..d4c52e92e0 100644
--- a/src/wp-includes/class-wp-theme-json.php
+++ b/src/wp-includes/class-wp-theme-json.php
@@ -2647,6 +2647,7 @@ class WP_Theme_JSON {
 	 * @since 6.1.0
 	 * @since 6.6.0 Setting a min-height of HTML when root styles have a background gradient or image.
 	 *              Updated general global styles specificity to 0-1-0.
+	 *              Fixed custom CSS output in block style variations.
 	 *
 	 * @param array $block_metadata Metadata about the block to get styles for.
 	 *
@@ -2662,6 +2663,7 @@ class WP_Theme_JSON {
 
 		// If there are style variations, generate the declarations for them, including any feature selectors the block may have.
 		$style_variation_declarations = array();
+		$style_variation_custom_css   = array();
 		if ( ! empty( $block_metadata['variations'] ) ) {
 			foreach ( $block_metadata['variations'] as $style_variation ) {
 				$style_variation_node           = _wp_array_get( $this->theme_json, $style_variation['path'], array() );
@@ -2691,6 +2693,10 @@ class WP_Theme_JSON {
 
 				// Compute declarations for remaining styles not covered by feature level selectors.
 				$style_variation_declarations[ $style_variation['selector'] ] = static::compute_style_properties( $style_variation_node, $settings, null, $this->theme_json );
+				// Store custom CSS for the style variation.
+				if ( isset( $style_variation_node['css'] ) ) {
+					$style_variation_custom_css[ $style_variation['selector'] ] = $this->process_blocks_custom_css( $style_variation_node['css'], $style_variation['selector'] );
+				}
 			}
 		}
 		/*
@@ -2819,6 +2825,14 @@ class WP_Theme_JSON {
 		// 6. Generate and append the style variation rulesets.
 		foreach ( $style_variation_declarations as $style_variation_selector => $individual_style_variation_declarations ) {
 			$block_rules .= static::to_ruleset( ":root :where($style_variation_selector)", $individual_style_variation_declarations );
+			if ( isset( $style_variation_custom_css[ $style_variation_selector ] ) ) {
+				$block_rules .= $style_variation_custom_css[ $style_variation_selector ];
+			}
+		}
+
+		// 7. Generate and append any custom CSS rules pertaining to nested block style variations.
+		if ( isset( $node['css'] ) && ! $is_root_selector ) {
+			$block_rules .= $this->process_blocks_custom_css( $node['css'], $selector );
 		}
 
 		return $block_rules;