| Cardiff Scaffolding Limited | Extraterritorial | 2010 |
| Cardiff School Ltd | Education | 2025 |
| Cardiff Scintigraphics Limited | Professional & scientific | 1992 |
| Cardiff Security Ltd Ltd | Construction | 2022 |
| Cardiff Self Storage Limited | Professional & scientific | 1988 |
| Cardiff Signs Ltd | Manufacturing | 2009 |
| Cardiff Skin DOC Limited | Health & social care | 2025 |
| Cardiff Slate & Stone Ltd | Administrative & support | 2012 |
| Cardiff Smile Centre Limited | Health & social care | 2013 |
| Cardiff Soft Play Limited | Arts & recreation | 2013 |
| Cardiff Solutions Limited | Information & communication | 2023 |
| Cardiff Spice Ltd | Hospitality | 2018 |
| Cardiff Sports Ltd | Wholesale & retail | 2019 |
| Cardiff Sports Orthopaedics LLP | | 2008 |
| Cardiff Sportsgear Limited | Construction | 2007 |
| Cardiff Stays Limited | Hospitality | 2023 |
| Cardiff Steak House Ltd | Hospitality | 2017 |
| Cardiff Steels Ltd | Manufacturing | 2015 |
| Cardiff Steiner Early Years Centre Limited | Education | 2012 |
| Cardiff Steiner School Limited | Education | 2012 |
| Cardiff Stone Ltd | Manufacturing | 2019 |
| Cardiff Stores Ltd | Wholesale & retail | 2024 |
| Cardiff Student Properties Ltd | Real estate | 2024 |
| Cardiff Super Cleaners Limited | Administrative & support | 2025 |
| Cardiff Taxis Ltd | Transport & logistics | 2025 |
| Cardiff Television Ltd | Arts & recreation | 1987 |
| Cardiff Theatrical Services Limited | Arts & recreation | 1983 |
| Cardiff Third Sector Council (C3SC) | Other services | 1997 |
| Cardiff Tiles Ltd | Wholesale & retail | 2025 |
| Cardiff Tints Limited | Other services | 2019 |
| Cardiff Trade Sales Limited | Wholesale & retail | 2006 |
| Cardiff Trail Runners Limited | Education | 2025 |
| Cardiff Transport Ltd | Transport & logistics | 2018 |
| Cardiff Transporters LLP | | 2018 |
| Cardiff Travelz Ltd. | Administrative & support | 2014 |
| Cardiff Treatment Rooms Limited | Health & social care | 2019 |
| Cardiff Tree Surgery Limited | Agriculture & fishing | 2021 |
| Cardiff Treescapes Arboricultural Contractors Limited | Administrative & support | 2013 |
| Cardiff Tyre Shop Ltd | Wholesale & retail | 2020 |
| Cardiff Ultrasound Clinic Ltd | Health & social care | 2025 |
| Cardiff Umbrella CIC | Arts & recreation | 2023 |
| Cardiff Union Services Limited | Wholesale & retail | 1988 |
| Cardiff University Students' Union | Education | 2010 |
| Cardiff Urology Care Ltd | Health & social care | 2024 |
| Cardiff Vale Hideaway Ltd | Real estate | 2025 |
| Cardiff Vehicle Services Ltd | Wholesale & retail | 2025 |
| Cardiff Vehicle Test Centre (ATF) Limited | Wholesale & retail | 2011 |
| Cardiff Vineyard | Other services | 2008 |
| Cardiff Violins Ltd | Wholesale & retail | 2023 |
| Cardiff Walk Apartments Limited | Real estate | 2015 |
| Cardiff Waste Limited | Water & waste | 1991 |
| Cardiff Wellness Centre Ltd | Health & social care | 2024 |
| Cardiff Wellness Lounge Ltd | Health & social care | 2024 |
| Cardiff Window Cleaning Limited | Administrative & support | 2018 |
| Cardiff Windows and Doors Ltd | Construction | 2011 |
| Cardiff Windows Ltd | Construction | 2013 |
| Cardiff Wine Events Ltd | Administrative & support | 2020 |
| Cardiff Women Healthcare Limited | Health & social care | 2019 |
| Cardiff Young Men's Christian Association | Other services | 2012 |
| Cardiffoods Ltd | Hospitality | 2025 |
| Cardiffremovalandstorage Limited | Transport & logistics | 2025 |
| Cardiffseedbank Ltd | Wholesale & retail | 2020 |
| Cardiffsofafurniture Ltd | Manufacturing | 2023 |
| Cardigan Court Limited | Households | 1989 |
| Cardik Mart Ltd | Wholesale & retail | 2026 |
| Cardinal Films Ltd | Information & communication | 2019 |
| Cardioid Holdings Ltd | Real estate | 2025 |
| Cardiolume Ltd | Professional & scientific | 2025 |
| Cardionyx Ltd | Education | 2025 |
| Cardiothoracic Imaging Ltd | Health & social care | 2021 |
| Cardo (South) Limited | Real estate | 2006 |
| Cardo (Wales & West) Limited | Construction | 2012 |
| Cardo Group Limited | Financial services | 2015 |
| Cardsynk Limited | Information & communication | 2017 |
| Cardworks Ltd | Manufacturing | 1975 |
| Care & Repair Cardiff and the Vale | Other services | 2015 |
| Care & Repair Cymru 2015 | Other services | 2015 |
| Care & Repair Home Improvement Services Ltd | Construction | 2016 |
| Care 33 Ltd | Professional & scientific | 2019 |
| Care a LOT Care Ltd | Health & social care | 2019 |
| Care Apothics Ltd | Professional & scientific | 2022 |
| Care Crew (Swansea) Limited | Administrative & support | 2023 |
| Care Crew Global Ltd | Financial services | 2019 |
| Care Crew Healthcare Limited | Administrative & support | 2021 |
| Care Crew Holdings Limited | Financial services | 2023 |
| Care Crew Limited | Other services | 2018 |
| Care Environmental Surveying Ltd | Construction | 2017 |
| Care Forward Nursing Solutions Limited | Health & social care | 2018 |
| Care Funding Guidance Ltd | Information & communication | 2014 |
| Care Hearted Oxfordshire Ltd | Education | 2021 |
| Care Home Action Group Limited | Financial services | 2022 |
| Care Home Investments LLP | | 2008 |
| Care Hub Lockers Ltd | Administrative & support | 2026 |
| Care in Cymru Ltd | Health & social care | 2015 |
| Care Logic Touch Ltd | Information & communication | 2025 |
| Care Managers Ltd | Administrative & support | 2019 |
| Care N Care Ltd | Health & social care | 2019 |
| Care Nation 24 Limited | Health & social care | 2025 |
| Care of Souls Homecare and Supported Living Ltd | Health & social care | 2024 |
| Care Optimum Ltd | Administrative & support | 2019 |