Yes, WooCommerce is free to use with WordPress. WooCommerce’s official site says it costs nothing to add Woo to a WordPress site, and the core plugin is available as open-source software for WordPress users.
However, running a WooCommerce store may still involve other costs. You may need to pay for web hosting, a domain name, premium themes, paid extensions, payment gateway fees, or shipping and marketing tools. WooCommerce itself is free, but your total store cost depends on the features and services you choose. That means you can start free with the plugin, then add paid tools only when your store needs them.