| Træg Trønder AS | Wholesale & retail | 2012 |
| Træsh Forlag Da | Information & communication | 2019 |
| Trøndelag Bil AS | Wholesale & retail | 2018 |
| Trøndelag Bilhjelp Trondheim AS | Transport & logistics | 2018 |
| Trøndelag Brønnboring AS | Construction | 2007 |
| Trøndelag Elektroprodukter AS | Manufacturing | 1988 |
| Trøndelag Expressen AS | Transport & logistics | 2024 |
| Trøndelag Freseservice AS | Construction | 2022 |
| Trøndelag Ortopediske Verksted AS | Health & social care | 2004 |
| Trøndelag Reiseliv AS | Administrative & support | 1991 |
| Trøndelag Rådgiving AS | Professional & scientific | 1993 |
| Trøndelag Tak AS | Construction | 2018 |
| Trøndelag Teater AS | Arts & recreation | 1937 |
| Trøndelag Vaktmesterservice AS | Administrative & support | 2021 |
| Trøndelag Varmepumpeservice AS | Construction | 2025 |
| Trøndelagkraft AS | Energy | 1998 |
| Trønder Bilglass AS | Other services | 2023 |
| Trønder Blomst AS | Wholesale & retail | 1995 |
| Trønder Partner AS | Wholesale & retail | 2005 |
| Trønder Taxi AS | Transport & logistics | 1993 |
| Trønderbad AS | Construction | 2018 |
| Trønderbil AS | Other services | 2011 |
| Trønderbryggeriet AS | Wholesale & retail | 1998 |
| Trønderburger AS | Hospitality | 2021 |
| Trønderburger Lager 11 AS | Hospitality | 2026 |
| Trønderdekk Leangen AS | Wholesale & retail | 2023 |
| Trøndereiendom AS | Real estate | 1992 |
| Trønderenergi AS | Energy | 1998 |
| Trønderenergi Kraft AS | Energy | 1997 |
| Trønderenergi Kraft Holding AS | Energy | 2022 |
| Trønderenergi Vekst Holding AS | Energy | 2022 |
| Trønderhopp Aktivitet AS | Real estate | 2014 |
| Trønderklima AS | Construction | 2023 |
| Trønderlys AS | Wholesale & retail | 1990 |
| Trønderlås AS | Other services | 2022 |
| Trøndermobil AS | Administrative & support | 2024 |
| Trøndern AS | Real estate | 2025 |
| Trønderskilt AS | Manufacturing | 1998 |
| Trøndersport AS | Professional & scientific | 2011 |
| Trønderstål Holding AS | Real estate | 2010 |
| Trøndertaxi Drift AS | Transport & logistics | 2026 |
| Trøndertaxi Eiendom AS | Real estate | 2026 |
| Trøndertekno AS | Administrative & support | 2025 |
| Trøndertransport AS | Transport & logistics | 2000 |
| Trønsdal Farvehandel AS | Wholesale & retail | 2024 |
| TS Maskin AS | Construction | 2013 |
| TS Pukkverk-Service AS | Manufacturing | 2020 |
| TS Utbygging AS | Real estate | 2022 |
| Ts&Lk Bassengdrift AS | Real estate | 2017 |
| Tsar AS | Health & social care | 2021 |
| Tschjetne Invest AS | | 2022 |
| TSL Invest AS | Wholesale & retail | 2013 |
| TST Trondheim Skjæreteknikk AS | Manufacturing | 2014 |
| TSW Holding AS | Real estate | 2014 |
| TT Forsikring Og Finans Trondheim AS | | 2018 |
| TT Holding Trondheim AS | Real estate | 2024 |
| TT3S Eiendom AS | Real estate | 2021 |
| Tta Invest AS | Financial services | 2005 |
| Ttbjj Merch AS | Wholesale & retail | 2023 |
| Tte Invest AS | Professional & scientific | 2017 |
| TTJ Holding AS | | 2017 |
| TTM 61 AS | | 2023 |
| TTS Norge AS | Administrative & support | 2005 |
| TTS Skulptursamling AS | Arts & recreation | 2020 |
| Ttu Invest AS | Professional & scientific | 2009 |
| Tuft Tech AS | | 2024 |
| Tuma Invest AS | | 2017 |
| Tun a Vest AS | Real estate | 2025 |
| Tun a Øst AS | Real estate | 2025 |
| Tuna Laguna Ans | Arts & recreation | 2006 |
| Tunaal Partners AS | | 2026 |
| Tunga Bil AS | Wholesale & retail | 2014 |
| Tunga Holding AS | Real estate | 2016 |
| Tunga Næringsbygg AS | Real estate | 2023 |
| Tungasletta 10 AS | Real estate | 2006 |
| Tungasletta 12 AS | Real estate | 2017 |
| Tungasletta 2 AS | Real estate | 2013 |
| Tungasletta 7 AS | Real estate | 2026 |
| Tungasletta 8 AS | Real estate | 2008 |
| Tungasletta AS | Real estate | 1968 |
| Tungasletta Holding AS | | 2026 |
| Tungaveien 26 AS | Real estate | 2009 |
| Tungaveien 34 AS | Real estate | 2014 |
| Tungaveien 36 AS | Real estate | 2016 |
| Tungaveien 38 AS | Real estate | 2001 |
| Tunisea AS | Manufacturing | 2025 |
| Tunstad AS | Professional & scientific | 2026 |
| Tur AS | Financial services | 2013 |
| Tur Holding AS | | 2021 |
| Turbobit AS | Information & communication | 2018 |
| Turnip AS | | 2026 |
| Turo AS | Real estate | 2005 |
| Turriga Holding AS | | 2021 |
| Turtle Invest AS | Real estate | 2005 |
| Tussemyra Familiebarnehage Da | Education | 2005 |
| Tusvik Pulverlakk AS | Manufacturing | 2020 |
| Tutu AS | Professional & scientific | 2013 |
| Tuu 10 AS | Real estate | 2023 |
| Tuu 8 AS | Real estate | 2024 |
| Tuva Tøv Design AS | Wholesale & retail | 2014 |