| Welsh Contact Centre Forum Limited | Other services | 2004 |
| West Grove Consulting Ltd | Professional & scientific | 2022 |
| West Hampton Cowbridge Ltd | Wholesale & retail | 2025 |
| Westbourne Commercial Finance Ltd | Financial services | 2025 |
| Westbourne School (Penarth) Limited | Education | 2013 |
| Western Welding & Engineering Company Limited | Extraterritorial | 1952 |
| Western Welding Holdings Limited | Professional & scientific | 2010 |
| Westmon Holdings Ltd | Financial services | 2021 |
| Westwood Court (Penarth) Limited | Households | 1999 |
| Wheeland Residents Association Limited | Households | 1983 |
| Whill Developments Limited | Construction | 2024 |
| Whill Electrical and Mechanical Ltd | Construction | 2019 |
| Whitchurch Nationwide Ltd | Professional & scientific | 2008 |
| White Label Communications Limited | Information & communication | 2004 |
| Whitfield Jones Limited | Professional & scientific | 2018 |
| Wide Open Pictures Ltd | Information & communication | 2019 |
| Williams Property Development Ltd | Real estate | 2023 |
| Willmore’S 1938 Ltd | Hospitality | 2026 |
| Windsor (71) Properties (Penarth) Limited | Extraterritorial | 1999 |
| Wintle Associates Ltd | Households | 2022 |
| Wired Management Ltd | Hospitality | 2017 |
| Wishful Cuisine Limited | Hospitality | 2025 |
| Withial & Co Limited | Real estate | 2016 |
| Wltc (Penarth) Limited | Arts & recreation | 2020 |
| Wootzoo Limited | Information & communication | 2019 |
| Wotv Holdings Limited | Financial services | 2025 |
| WVS Independent (Cardiff) Ltd | Wholesale & retail | 2008 |
| WWS 1987 Ltd | Construction | 2006 |
| Wyndham Motors Limited | Wholesale & retail | 2012 |
| Xinlida Limited | Wholesale & retail | 2023 |
| Y Casgenau Ltd | Hospitality | 2022 |
| YA Pasta Ltd | Hospitality | 2026 |
| YA Souvlaki 2 Ltd | Hospitality | 2026 |
| Yaruku Limited | Education | 2023 |
| Year of the Dragon 3 Limited | Wholesale & retail | 2024 |
| Ymca (Barry) Residential Limited | Households | 2004 |
| Youbnb Limited | Real estate | 2018 |
| Your Storage Hub Ltd | Real estate | 2023 |
| Your Virtual Marketing Manager Limited | Professional & scientific | 2015 |
| YUM N' Bass Ltd | Hospitality | 2023 |
| Z&Z Property Management Limited | Real estate | 2023 |
| Zephyr E Publishing Ltd | Information & communication | 2024 |
| Zest Mortgages Ltd | Financial services | 2019 |
| Zowie Burge Aesthetics Limited | Other services | 2020 |
| ZY Consult Limited | Health & social care | 2019 |