| Storvask Mma AS | Other services | 1970 |
| Straumen Hageby Utvikling AS | Real estate | 2022 |
| Stunt Da | Administrative & support | 2000 |
| Styreweb Regnskap AS | Professional & scientific | 2018 |
| Ståpå AS | | 2026 |
| Stølhaug Drift AS | Real estate | 2003 |
| Sulland Trondheim AS | Other services | 1911 |
| Suttuøra AS | Real estate | 2007 |
| Svaberget AS | Real estate | 2012 |
| Svenn Arild Fiskvik AS | | 2005 |
| Systemrevisjon Syd AS | | 1993 |
| Sæterbakken 19 AS | Real estate | 2021 |
| Sæther Bedrifter AS | Transport & logistics | 2024 |
| Sæther Transport AS | Transport & logistics | 2024 |
| Søberg Bygg AS | Real estate | 2006 |
| Søbstad AS | Construction | 1965 |
| Søbstad Eiendom AS | Real estate | 2004 |
| Søbstad Holding AS | Construction | 2005 |
| Søra AS | Real estate | 2022 |
| Sørbyen Legesenter Da | Health & social care | 2006 |
| Sørbø Norge AS | Wholesale & retail | 2012 |
| T. K. Holding AS | | 2022 |
| Takgruppen AS | Construction | 2017 |
| Takråd a. Kalland AS | Professional & scientific | 2002 |
| Taksenteret AS | Wholesale & retail | 1997 |
| Taksenteret Eiendom AS | Real estate | 2007 |
| Taksenteret Holding AS | Wholesale & retail | 2019 |
| Takst 1 AS | Real estate | 2007 |
| Tal Salg AS | Administrative & support | 2024 |
| Tanner Entertainment AS | Arts & recreation | 2012 |
| Tannlege Hanne Mjøsund AS | Health & social care | 2017 |
| Tannlege Mattias Sterner AS | Health & social care | 2015 |
| Tannlege Steinar Kløve AS | Health & social care | 2003 |
| Tarbush AS | Hospitality | 2024 |
| Target Presentation AS | Professional & scientific | 1997 |
| Tasi AS | Professional & scientific | 2012 |
| Taxi U-226 AS | Transport & logistics | 2020 |
| Tea Holding AS | Professional & scientific | 2010 |
| Tec Media AS | Information & communication | 2022 |
| Tech Global AS | Information & communication | 2018 |
| Teto Grafiske AS | Manufacturing | 1989 |
| Textilia Group Norge AS | Other services | 1922 |
| Textilia Norge AS | Other services | 2003 |
| TGG Service AS | Administrative & support | 2016 |
| Thatglow.No AS | Wholesale & retail | 2022 |
| Theliver AS | | 2020 |
| Thyrum Inspection AS | Professional & scientific | 2015 |
| Tiar Eiendom AS | Real estate | 2022 |
| Tidy Account AS | Professional & scientific | 2010 |
| Tidy Development AS | Professional & scientific | 2023 |
| Tiller Fysioterapi Og Manuell Terapi AS | Health & social care | 2005 |
| Tiller Klokker & Smykker AS | Wholesale & retail | 2000 |
| Tiller Maskin Og Bygg AS | Construction | 2023 |
| Tiller Pizza AS | Manufacturing | 2019 |
| Tiller Specsavers AS | Wholesale & retail | 2020 |
| Tiller Tannhelse Da | Health & social care | 2011 |
| Tiller Utstyrsleie AS | Administrative & support | 2003 |
| Tiller-Grillen AS | Hospitality | 2025 |
| Tillerbyen Securities Holding AS | Real estate | 2006 |
| Tillertorget Legesenter AS | Health & social care | 2014 |
| Tiltaksvegen AS | Real estate | 2022 |
| Tim Rudi AS | Professional & scientific | 2021 |
| Tim Rudi Holding AS | Professional & scientific | 2021 |
| Tipi Holding AS | Real estate | 2016 |
| Tk-Service Trondheim AS | Wholesale & retail | 1989 |
| Tluk AS | Transport & logistics | 2026 |
| TNB CS AS | Wholesale & retail | 2018 |
| Tocon AS | Professional & scientific | 2022 |
| Tolob Holding AS | | 2022 |
| Tonerhuset AS | Wholesale & retail | 2011 |
| Tooly AS | Administrative & support | 2025 |
| Top Rod AS | Administrative & support | 2026 |
| Toppfag Invest AS | | 2019 |
| Tor Hatlen Invest AS | | 2025 |
| Tore Thrana Holding AS | Wholesale & retail | 2014 |
| Torgardstrøa 12 AS | Real estate | 2025 |
| Toy AS | Wholesale & retail | 2020 |
| Tradeway AS | Wholesale & retail | 1996 |
| Trafikkvakta Det Finn's Trafikkhjelp AS | Transport & logistics | 2001 |
| Trail Auto Maskin AS | Wholesale & retail | 2014 |
| Tran Eco AS | Financial services | 2013 |
| Trandersen Holding AS | | 2026 |
| Transportsentralen Trondheim AS | Transport & logistics | 2013 |
| Transportsentralen Trondheim Eiendom AS | Real estate | 2006 |
| Trio Eiendomsservice AS | Professional & scientific | 2009 |
| Triona AS | Information & communication | 1997 |
| Tronderenergi AS | Information & communication | 2019 |
| Trondheim Elektro AS | Construction | 2021 |
| Trondheim Event AS | Arts & recreation | 2024 |
| Trondheim Flyttebyrå AS | Transport & logistics | 2026 |
| Trondheim Hundehotell AS | Other services | 2022 |
| Trondheim Kunstgress Syd AS | Arts & recreation | 2000 |
| Trondheim Regnskapskontor AS | Professional & scientific | 1991 |
| Trondheim Storbilvask AS | Other services | 2013 |
| Trondheim Tak AS | Construction | 2005 |
| Trondheim Tak Holding AS | Real estate | 2011 |
| Trondheim Utleie AS | Real estate | 2017 |
| Trondheim Vaksinasjons Og Reisemedisinske Klinikk AS | Health & social care | 2000 |
| Trønder Oil AS | Wholesale & retail | 2012 |
| Trønderblikk AS | Construction | 1991 |