add_filter( 'add_to_cart_text', 'woo_custom_cart_button_text' ); // < 2.1 add_filter( 'woocommerce_product_single_add_to_cart_text', 'woo_custom_cart_button_text' ); // 2.1 + function woo_custom_cart_button_text() { return __( 'My Button Text', 'woocommerce' ); }