| Tannpleierklinikken AS | Health & social care | 2008 |
| Tassebekk Office Center AS | Real estate | 2015 |
| TCL AS | Financial services | 2005 |
| Team Duo AS | | 2023 |
| Team Fearless AS | | 2016 |
| Team Steine AS | Arts & recreation | 2023 |
| Technet AS | Information & communication | 1999 |
| Teft Design AS | Professional & scientific | 2014 |
| Teien Consult AS | Professional & scientific | 2024 |
| Teien Eiendom AS | Real estate | 2001 |
| Teien Jøssang Invest AS | | 2023 |
| Teknobingo Larvik AS | Arts & recreation | 2002 |
| Tele-Mat Ulefoss AS | Wholesale & retail | 2004 |
| Telegata 1 Notodden AS | Real estate | 2023 |
| TELELARS1 AS | Construction | 2022 |
| Telesenteret AS | Real estate | 2003 |
| Tema AS | Wholesale & retail | 1982 |
| Tema Eiendom AS | Real estate | 1989 |
| Tenvik Invest AS | Professional & scientific | 2016 |
| Tenvik Utvikling AS | Construction | 2022 |
| Terje Larsen VVS AS | Construction | 2005 |
| Terra Eiendom AS | Real estate | 2015 |
| TF Us 2 AS | | 2019 |
| Tf-Byggentreprenør AS | Construction | 2025 |
| TFP Blikk AS | Construction | 2024 |
| TH a Abrahamsen AS | Manufacturing | 1990 |
| TH Alviniussen AS | Wholesale & retail | 1977 |
| TH Atelier AS | Arts & recreation | 2023 |
| TH Håndverk AS | Construction | 2022 |
| The Cabinet AS | | 2019 |
| The Hair AS | Other services | 2017 |
| The Nordic VR Company AS | Wholesale & retail | 2017 |
| Therik AS | | 2016 |
| Thermocut AS | Wholesale & retail | 2007 |
| Thes Helse AS | Health & social care | 2018 |
| Thilesen Holding AS | Health & social care | 2014 |
| Tholfsen Regnskap AS | Professional & scientific | 1997 |
| Thor Eddy Eiendom AS | Real estate | 2023 |
| Thor Eddy Hansen AS | Transport & logistics | 1994 |
| Thoresen Transport Avd. Lastebil AS | Transport & logistics | 2012 |
| Thorshaug AS | Real estate | 2010 |
| Thtjl Holding AS | | 2026 |
| Thunberg Betong AS | Construction | 2025 |
| Thunberg Entreprenør AS | Construction | 2014 |
| Tibre Holding AS | | 2025 |
| Tiebreak Holding AS | Real estate | 2019 |
| Tiger Eiendom Industriveien Da | Real estate | 2009 |
| Tilsig AS | Information & communication | 2021 |
| Tingee AS | Professional & scientific | 2023 |
| Tinnvest AS | Real estate | 1999 |
| Tiur Holding AS | Real estate | 1999 |
| Tjodalph Holding AS | Financial services | 2017 |
| Tjølling Grillen AS | Hospitality | 2012 |
| Tjøme Næringsutvikling AS | Real estate | 1979 |
| TK Invest Holding AS | Wholesale & retail | 2018 |
| TKL Holding AS | | 2026 |
| Tltr Capital AS | | 2021 |
| TNB Larvik AS | Wholesale & retail | 2002 |
| Tni Invest AS | | 2021 |
| Toc 3 AS | Real estate | 1987 |
| Toda AS | Professional & scientific | 2005 |
| Tol AS | Financial services | 2017 |
| Tom Hvaal AS | Construction | 1995 |
| Toma Bøker AS | Information & communication | 2023 |
| Tommy Holtan AS | Wholesale & retail | 1999 |
| Tomta-Eiendom AS | Real estate | 2013 |
| Tomter Holding AS | | 2025 |
| Toogtyve AS | Professional & scientific | 2021 |
| Tor Erling Andersen AS | Construction | 1989 |
| Torbjørn Invest AS | Real estate | 2009 |
| Torgbua Ans - Magnussen & Mørk | Hospitality | 1989 |
| Torget 1 Larvik AS | Real estate | 2022 |
| Torget 11 Larvik AS | Real estate | 2026 |
| Torget 3 Larvik AS | Real estate | 2005 |
| Torget 5 Larvik AS | Real estate | 2020 |
| Torget 8 a AS | Real estate | 2012 |
| Torget Medisinske Senter AS | Health & social care | 2015 |
| Torget Parfymeri Da | Wholesale & retail | 2002 |
| Torkrise Holding AS | | 2021 |
| Tormatic AS | Wholesale & retail | 2001 |
| Tormatic Holding AS | Wholesale & retail | 2005 |
| Torstrand Energistasjon AS | Wholesale & retail | 2022 |
| Torstrand Grill Og Pizza AS | Hospitality | 2021 |
| Torstvedt Syd AS | Real estate | 2015 |
| Torstvedtbakken AS | Real estate | 2009 |
| Torsvang AS | Real estate | 2010 |
| Torsvang Eiendom AS | Real estate | 1998 |
| Torsvang Utvikling AS | Real estate | 2026 |
| Torvet 8 AS | Real estate | 1995 |
| Torvet Holding AS | | 2005 |
| Totalpac AS | Real estate | 2002 |
| TP Møbler AS | Wholesale & retail | 2018 |
| TPS Eiendom AS | Manufacturing | 2012 |
| TPS Group AS | Manufacturing | 2012 |
| Tradetec Holding AS | Real estate | 2005 |
| Traktor Transport AS | Construction | 2002 |
| Transactions AS | Information & communication | 2016 |
| Transmisjonssystem AS | Wholesale & retail | 2006 |
| Transmisjonsteknikk AS | Wholesale & retail | 2005 |
| Transportsenter Larvik AS | Transport & logistics | 2018 |