| Trondheim Padelsenter AS | Real estate | 2018 |
| Trondheim Parinvest Holding AS | Real estate | 2012 |
| Trondheim Parkering AS | Transport & logistics | 2018 |
| Trondheim Performance Center AS | Arts & recreation | 2025 |
| Trondheim Pizza AS | Hospitality | 2020 |
| Trondheim Postgård Da | Real estate | 2001 |
| Trondheim Private Legekontor AS | Health & social care | 2014 |
| Trondheim Private Musikkskole AS | Education | 2011 |
| Trondheim Private Omsorgstjeneste AS | Health & social care | 2007 |
| Trondheim Properties AS | Real estate | 2019 |
| Trondheim Properties I AS | Real estate | 2022 |
| Trondheim Psykologsenter AS | Health & social care | 2021 |
| Trondheim Ramm AS | Wholesale & retail | 2020 |
| Trondheim Real Estate AS | Real estate | 2019 |
| Trondheim Reeferservice Ans | Construction | 2002 |
| Trondheim Ridesenter AS | Education | 2026 |
| Trondheim Rørservice AS | Construction | 2023 |
| Trondheim Service-Verksted AS | Other services | 2026 |
| Trondheim Skalldyr AS | Agriculture & fishing | 2021 |
| Trondheim Slaktehus AS | Manufacturing | 2015 |
| Trondheim Spektrum AS | Administrative & support | 1991 |
| Trondheim Spektrum Eiendom AS | Real estate | 1962 |
| Trondheim Stage AS | Arts & recreation | 2018 |
| Trondheim Stasjonssenter AS | Real estate | 2013 |
| Trondheim Sykkelservice AS | Other services | 2025 |
| Trondheim Sysenter AS | Wholesale & retail | 2005 |
| Trondheim Systemutvikling AS | Information & communication | 2012 |
| Trondheim Tak Og Fasade AS | Construction | 1994 |
| Trondheim Tannregulering AS | Health & social care | 2013 |
| Trondheim Taxi AS | Transport & logistics | 2012 |
| Trondheim Taxi Tel AS | Transport & logistics | 2021 |
| Trondheim Tek AS | Manufacturing | 2023 |
| Trondheim Tekniske Verksted AS | Administrative & support | 2003 |
| Trondheim Thaimat AS | Hospitality | 2018 |
| Trondheim Thereminorkester Ans | Arts & recreation | 2007 |
| Trondheim Topphåndball AS | Arts & recreation | 2022 |
| Trondheim Torg Frisør AS | Other services | 1992 |
| Trondheim Trafikkskole AS | Education | 2012 |
| Trondheim Trefelling AS | Administrative & support | 2022 |
| Trondheim Utvikling Og Eiendom AS | Real estate | 2013 |
| Trondheim Vask- Og Renseri AS | Other services | 1991 |
| Trondheim Ventilasjon AS | Construction | 2021 |
| Trondheim Verktøysenter Elma AS | Wholesale & retail | 2019 |
| Trondheim Videregående Steinerskole AS | Education | 2024 |
| Trondheim Works AS | Professional & scientific | 2022 |
| Trondheim Øst Eiendomsmegling AS | Real estate | 2013 |
| Trondheim Øst Utbygging AS | Real estate | 2024 |
| Trondheim Øyelegesenter AS | Health & social care | 1990 |
| Trondheimsgynekologene AS | Health & social care | 2023 |
| Trondheimsnaprapatene AS | Arts & recreation | 2013 |
| Trondheimsrestaurantene Ans | Professional & scientific | 1996 |
| Trondheimstannlegene AS | Health & social care | 2019 |
| Trondheimsterminalen AS | Transport & logistics | 2013 |
| Trondhjem Bolig AS | Construction | 2021 |
| Trondhjem Eiendom AS | Real estate | 2024 |
| Trondhjem Mikrobryggeri AS | Hospitality | 1998 |
| Trondhjem Utleie AS | Real estate | 2021 |
| Trondhjems Fotterapi AS | Health & social care | 2020 |
| Trondhjems Seilforening Havn AS | Transport & logistics | 1999 |
| Trondhjemsbygg Eiendom Ans | Real estate | 2000 |
| Trondhjemsvandringer Da | Administrative & support | 2025 |
| Trondhjæm Eiendom AS | Real estate | 2002 |
| Trondos AS | Real estate | 2016 |
| Tronds Interesser AS | Real estate | 2011 |
| Tronfjord Consult AS | Information & communication | 2024 |
| Tronsaune VVS AS | Construction | 2001 |
| Tronslien Holding AS | | 2026 |
| Tronstad & Tømmervik Invest Da | | 1999 |
| Tronstad Estudio Ans | Information & communication | 2000 |
| Trontek AS | Manufacturing | 1986 |
| Tropical Food AS | Wholesale & retail | 2020 |
| Troset Holding AS | Real estate | 2007 |
| Troset Invest AS | Arts & recreation | 2002 |
| Trotan AS | Manufacturing | 2016 |
| Trovare AS | Hospitality | 2012 |
| TRS- Trøndelag Renholds Service AS | Administrative & support | 2022 |
| Trubadudes Da | Arts & recreation | 2025 |
| Trucktech Midt AS | Wholesale & retail | 2019 |
| Trueblue AS | | 2021 |
| Trulli Sogno AS | | 2026 |
| Truls Johansen AS | Professional & scientific | 2018 |
| Trust Holding AS | Financial services | 2011 |
| Trust IT. AS | Information & communication | 2005 |
| Trustify AS | Professional & scientific | 2025 |
| Truzt Holding AS | Wholesale & retail | 2025 |
| Tryg Elektro AS | Administrative & support | 2022 |
| Tryg Holding AS | Administrative & support | 2024 |
| Trygg Revisjon AS | Professional & scientific | 2018 |
| Trygg Varsel AS | Wholesale & retail | 2026 |
| Tryggbo AS | Health & social care | 2000 |
| Tryggest AS | | 2022 |
| Tryggvason Bygg Og Montasje AS | Construction | 2017 |
| Tryggvason Drift Og Forvaltning AS | Real estate | 2024 |
| Tryggvason Holding AS | Real estate | 2005 |
| Trygt Fram AS | Transport & logistics | 2026 |
| Trym AS | Real estate | 2018 |
| Trym Eiendom AS | Real estate | 2012 |
| Trysil Hotellutvikling AS | Real estate | 2004 |
| Trysil Suiter AS | Real estate | 2007 |
| Trål Invest AS | | 2025 |