| Tannlege Stig Rune Meland AS | Health & social care | 2012 |
| Tannlegene I Cappelens Gate AS | Health & social care | 2026 |
| Tannlegene I Cappelens Gate Da | Health & social care | 2003 |
| Tannlegene I Kaffehuset AS | Health & social care | 2024 |
| Tannlegene Nikolaisen AS | Health & social care | 2025 |
| Tanntekniker Arnestad AS | Manufacturing | 2020 |
| Tapethuset Ans | Wholesale & retail | 1990 |
| Taraxa AS | Professional & scientific | 2023 |
| Tassen AS | Construction | 2019 |
| Tata Steel Norway Byggsystemer AS | Manufacturing | 1990 |
| Tatte AS | Health & social care | 2021 |
| Taxare AS | Professional & scientific | 2004 |
| Taxi Transport Telemark AS | Transport & logistics | 1994 |
| Taxi Transport Telemark Eiendom AS | Real estate | 2008 |
| TB Hauen Invest AS | | 2023 |
| TB Taksikring AS | Manufacturing | 1995 |
| TBC AS | Construction | 2009 |
| Tbholding AS | Professional & scientific | 2011 |
| TD Eiendom AS | Real estate | 2013 |
| Tdi 24H Criticalexpress AS | Transport & logistics | 2005 |
| Te Eiendomservice AS | Construction | 2023 |
| Team Bil AS | Wholesale & retail | 2020 |
| Team X AS | Construction | 2020 |
| Teateret Ditt AS | Arts & recreation | 2018 |
| Teatertips Jensen Og Engh Da | Arts & recreation | 2001 |
| Tech-Qw AS | Professional & scientific | 2018 |
| Techpack AS | Wholesale & retail | 2015 |
| Teco Electronics AS | Manufacturing | 1993 |
| Tecta Invest AS | | 1966 |
| Teige Bøe Holding AS | Financial services | 2005 |
| Tekar Holding AS | Real estate | 2018 |
| Teksas Holding AS | Financial services | 2008 |
| Tel Pa AS | Professional & scientific | 2022 |
| Telecom AS | Real estate | 1975 |
| Telegas Øst AS | Wholesale & retail | 2022 |
| Telegruppen AS | Professional & scientific | 2023 |
| Telemark Augeklinikk AS | Health & social care | 2024 |
| Telemark Avløpsrensing AS | Construction | 2013 |
| Telemark Bil AS | Wholesale & retail | 2026 |
| Telemark Bolig Teknikk AS | Wholesale & retail | 2012 |
| Telemark Brannteknikk AS | Professional & scientific | 2000 |
| Telemark Bygg Nuf | Construction | 2005 |
| Telemark Byggeiendom AS | Real estate | 2020 |
| Telemark Eiendom AS | Real estate | 2015 |
| Telemark Eiendomsmegling AS | Real estate | 2020 |
| Telemark Eiendomsmegling Holding AS | Real estate | 2021 |
| Telemark Endoskopiklinikk AS | Health & social care | 2019 |
| Telemark Energispar AS | Construction | 2002 |
| Telemark Flis Og Bygg AS | Construction | 2026 |
| Telemark Flytteservice Ans | Transport & logistics | 2001 |
| Telemark Group AS | Administrative & support | 2012 |
| Telemark Gulvsliper AS | Construction | 2021 |
| Telemark Hesteklinikk AS | Professional & scientific | 2005 |
| Telemark HR & Rekruttering AS | Administrative & support | 2024 |
| Telemark Kjøkkensenter AS | Wholesale & retail | 2026 |
| Telemark Kobber Og Blikk AS | Construction | 2005 |
| Telemark Kobber Og Blikk Da | Construction | 2001 |
| Telemark Laser AS | Other services | 2018 |
| Telemark Malerservice Ans | Construction | 1991 |
| Telemark Massemottak AS | Water & waste | 2019 |
| Telemark Motor Service AS | Manufacturing | 2022 |
| Telemark Nevrosenter AS | Health & social care | 2021 |
| Telemark Og Vestfold Bilutleie AS | Administrative & support | 2013 |
| Telemark Og Vestfold Eiendom AS | Real estate | 2015 |
| Telemark Og Vestfold Regionteater AS | Arts & recreation | 1978 |
| Telemark Områdesikring AS | Construction | 2013 |
| Telemark Opplagssenter AS | Real estate | 2012 |
| Telemark Park & Hageanlegg AS | Administrative & support | 2008 |
| Telemark Prosjektutvikling AS | Real estate | 2006 |
| Telemark Pukk Og Grus AS | Mining & quarrying | 2022 |
| Telemark Settefisk AS | Agriculture & fishing | 2004 |
| Telemark Sinfonietta SA | Arts & recreation | 2010 |
| Telemark Software Solutions AS | Information & communication | 2025 |
| Telemark Spas AS | Wholesale & retail | 2019 |
| Telemark System Rør AS | Manufacturing | 2014 |
| Telemark Takst Og Byggvurdering AS | Professional & scientific | 2008 |
| Telemark Takst Og Eiendom AS | Construction | 1999 |
| Telemark Takstforum AS | Professional & scientific | 2026 |
| Telemark Taxi AS | Transport & logistics | 2004 |
| Telemark Terreng Og Kraftservice AS | Agriculture & fishing | 2016 |
| Telemark Toppidrett Ungdomsskole Skien AS | Education | 2015 |
| Telemark Toto AS | Arts & recreation | 1997 |
| Telemark Trade Company AS | Wholesale & retail | 2004 |
| Telemark Utvikling AS | Real estate | 2020 |
| Telemark Vaksinasjonssenter AS | Health & social care | 2001 |
| Telemark Varmepumpe Service AS | Construction | 2025 |
| Telemark Veisikring AS | Construction | 2024 |
| Telemark Ventilasjonsservice AS | Construction | 2021 |
| Telemarkhus AS | Construction | 1991 |
| Telemarkhus Holding AS | Construction | 2005 |
| Telemarkhus Utvikling AS | Construction | 1998 |
| Telemarksavisa AS | Information & communication | 1989 |
| Telemarksgata 1 Skien AS | Real estate | 2018 |
| Telemarksgata 12 AS | Real estate | 2008 |
| Telemarksgata 14 AS | Real estate | 2009 |
| Telemarksgata 4 AS | Real estate | 1976 |
| Telemarksgata 8 AS | Real estate | 1990 |
| Telemarksgaten 10 AS | Real estate | 2006 |
| Telemarksgt 11 AS | Real estate | 2014 |
| Telescope AS | Information & communication | 1996 |