| 3I IIF GP LLP | | 2020 |
| 3I India Infrastructure Fund a LP | | 2007 |
| 3I India Infrastructure Fund B LP | | 2007 |
| 3I India Infrastructure Fund C LP | | 2007 |
| 3I India Infrastructure Fund D LP | | 2007 |
| 3I Infotech (UK) Limited | Information & communication | 2004 |
| 3I Infrastructure 2005-06 LP | | 2005 |
| 3I Infrastructure Seed Assets LP | | 2007 |
| 3I International Holdings | Professional & scientific | 1945 |
| 3I International Services PLC | Financial services | 2001 |
| 3I Investments PLC | Financial services | 2000 |
| 3I IP Acquisitions GP LLP | | 2020 |
| 3I IP Acquisitions Limited | Financial services | 2020 |
| 3I IP Acquisitions LP | | 2020 |
| 3I Javelin H1A LP | | 2013 |
| 3I Javelin H1B LP | | 2013 |
| 3I Klara C1 LP | | 2015 |
| 3I Lilas S1 LP | | 2016 |
| 3I Managed Infrastructure Acquisitions GP (2017) LLP | | 2016 |
| 3I Managed Infrastructure Acquisitions GP Limited | Financial services | 2016 |
| 3I Managed Infrastructure Acquisitions II LP | | 2026 |
| 3I Managed Infrastructure Acquisitions LP | | 2016 |
| 3I MIA Holdings Limited | Financial services | 2017 |
| 3I MIA II GP (2026) Limited | Financial services | 2026 |
| 3I Mito S1A LP | | 2014 |
| 3I Mito S1B LP | | 2014 |
| 3I Music Limited | Administrative & support | 2012 |
| 3I Networks Finland LP | | 2011 |
| 3I Networks Sweden LP | | 2015 |
| 3I Nominees Limited | Financial services | 1994 |
| 3I Nordic PLC | Financial services | 2001 |
| 3I Nordic Private Equity 2004-06 LP | | 2004 |
| 3I Optics Ltd | Manufacturing | 2016 |
| 3I Osprey GP Limited | Financial services | 2007 |
| 3I Osprey Limited Partnership | | 2007 |
| 3I Oystercatcher Holdco Limited | Financial services | 2025 |
| 3I PAN European Buy-Outs 2004-06 LP | | 2004 |
| 3I PAN European Growth Capital 2005-06 LP | | 2005 |
| 3I Parallel Ventures LP | | 1997 |
| 3I PE 2013-16A LP | | 2013 |
| 3I PE 2013-16B LP | | 2013 |
| 3I PE 2013-16C LP | | 2013 |
| 3I PE 2016-19A LP | | 2016 |
| 3I PE 2016-19B LP | | 2016 |
| 3I PE 2019-22 a LP | | 2019 |
| 3I PE 2019-22 B LP | | 2019 |
| 3I PE 2022-25 a LP | | 2022 |
| 3I PE 2022-25 B LP | | 2022 |
| 3I PE 2025-28 a LP | | 2025 |
| 3I PE 2025-28 B LP | | 2025 |
| 3I PE 2025-28 C LP | | 2025 |
| 3I PLC | Financial services | 1945 |
| 3I Primary Infrastructure 2005-06 LP | | 2005 |
| 3I Racing B1 LP | | 2017 |
| 3I Rail Investments LP | | 2015 |
| 3I SCI Holdings Limited | Financial services | 2018 |
| 3I Spain Private Equity 2004-06 LP | | 2004 |
| 3I Tampnet Holdings Limited | Financial services | 2019 |
| 3I UK Investment Partners | | 1996 |
| 3I UK Private Equity 2004-06 LP | | 2004 |
| 3I Vision a LP | | 2018 |
| 3I Vision Ltd | Information & communication | 2020 |
| 3I Vision N LP | | 2018 |
| 3I Zephyr a L.P. | | 2022 |
| 3I Zephyr B L.P. | | 2022 |
| 3I Zephyr GP (2022) Limited | Financial services | 2022 |
| 3I-FITNESS Ltd | Arts & recreation | 2021 |
| 3IAM Ltd | Health & social care | 2016 |
| 3IC Solutions Limited | Professional & scientific | 2019 |
| 3IN Attero Holdco Limited | Financial services | 2020 |
| 3IN MIA II Holdco Limited | Financial services | 2026 |
| 3INT Limited | Information & communication | 2022 |
| 3INUKAY Ltd | Wholesale & retail | 2026 |
| 3ISEC Limited | Information & communication | 2017 |
| 3IVE Limited | Professional & scientific | 2025 |
| 3J Business Solutions Limited | Information & communication | 2006 |
| 3J Digital Ltd | Information & communication | 2026 |
| 3J Finance Limited | Administrative & support | 2008 |
| 3J Nails & Beauty Limited | Other services | 2015 |
| 3J Props Ltd | Real estate | 2019 |
| 3J Real Estate Ltd | Real estate | 2018 |
| 3J2 Discoveries Ltd | Wholesale & retail | 2020 |
| 3JANE Limited | Administrative & support | 2023 |
| 3JC Capital Limited | Other services | 2019 |
| 3JC Properties UK Limited | Real estate | 2025 |
| 3JG Limited | Professional & scientific | 2025 |
| 3JNOBLE Management Services Ltd | Professional & scientific | 2018 |
| 3JRD Traders Ltd | Wholesale & retail | 2021 |
| 3JT Ltd | Manufacturing | 2019 |
| 3JU Ltd | Real estate | 2016 |
| 3K Art House Ltd | Arts & recreation | 2023 |
| 3K Casa Ltd | Construction | 2020 |
| 3K Financial & Accounting Services Ltd | Professional & scientific | 2022 |
| 3K Holdings Investments UK Limited | Financial services | 2025 |
| 3K Home and Furniture Ltd | Manufacturing | 2023 |
| 3K Supply Ltd | Wholesale & retail | 2026 |
| 3K0 Architectural Design Ltd | Professional & scientific | 2021 |
| 3K3 UK Ltd | Information & communication | 2020 |
| 3KC (Corporate Services) Limited | Administrative & support | 2026 |
| 3KENT Transporation Ltd | Transport & logistics | 2025 |