| Tulkkaus Silmu Oy | Professional & scientific | 2020 |
| Tulkkauspalvelu Arvo Oy | Professional & scientific | 2013 |
| Tulkkauspalvelu Linkki Oy | Professional & scientific | 2016 |
| Tulkkauspalvelu Seppälä Oy | Professional & scientific | 2024 |
| Tulkkauspalvelut MaJSign Oy | Professional & scientific | 2025 |
| Tulkki- ja kommunikaatiopalvelut Puheenvuoro OY | Professional & scientific | 2015 |
| Tullifon Oy | Professional & scientific | 1998 |
| TuloTalo Oy | Professional & scientific | 2023 |
| Tulos-Jyvä Oy | Financial services | 1992 |
| Tuloskiinteistöt Oy | Real estate | 2015 |
| Tuloskone Oy | Real estate | 1987 |
| Tulosmittaus Leino Oy | Professional & scientific | 2017 |
| Tulosmylly Oy | Professional & scientific | 2003 |
| Tulostoimi Oy | Wholesale & retail | 1933 |
| Tunedafone Oy | Information & communication | 2005 |
| Tunne Mielesi Oy | Health & social care | 2020 |
| Tunnepuhe Oy | Health & social care | 2024 |
| Tunturi Oy Ltd | Wholesale & retail | 1941 |
| Tunturi Trading Oy | Financial services | 2025 |
| TunturiBurger Oy | Hospitality | 2012 |
| Tuojani Oy | Other services | 2023 |
| Tuoketo Oy | Real estate | 1988 |
| Tuokkola Solutions Oy | Professional & scientific | 2025 |
| Tuomas Gee OY | Other services | 2016 |
| Tuomas Grönman Oy | Health & social care | 2010 |
| Tuomas Tunturi Oy | Financial services | 2016 |
| Tuomed Oy | Health & social care | 2013 |
| Tuomiahde Oy | Professional & scientific | 2022 |
| Tuomikoski Legal Oy | Professional & scientific | 2022 |
| Tuomiopäivä Events Oy | Arts & recreation | 2020 |
| Tuomo's Games Oy | Information & communication | 2020 |
| Tuoriniemi Dream Oy | Manufacturing | 1999 |
| Tuotantoyhtiö Encore Oy | Arts & recreation | 2023 |
| Tuotantoyhtiö Koti Osk | Arts & recreation | 2009 |
| Tuotekuljetus Numminen Oy | Transport & logistics | 1985 |
| Tuotesuunnittelu TT Oy | Professional & scientific | 2021 |
| Tuottajaryhmä Psykomedia Oy | Health & social care | 1987 |
| Tuottokoivu Oy | Financial services | 2009 |
| Tupla A Oy | Hospitality | 2025 |
| TuplaBurger Oy | Hospitality | 2008 |
| Tupocon Oy | Construction | 1998 |
| Turboathe Oy Ab | Other services | 2025 |
| Turbulentti Oy | Other services | 2022 |
| Turkami Oy | Financial services | 2002 |
| Turkka Lastunen Consulting Oy Ltd | Professional & scientific | 2016 |
| Turku Audit Oy | Professional & scientific | 2025 |
| Turku Beauty Institute Oy Ltd | Education | 2007 |
| Turku Cargo Service Oy | Transport & logistics | 1997 |
| Turku City Data Oy | Information & communication | 2019 |
| Turku Curling Arena Oy | Arts & recreation | 2016 |
| Turku Dental-Mill Oy | Manufacturing | 2013 |
| Turku Energia Sähköverkot Oy | Energy | 2005 |
| Turku Fiber Oy | Wholesale & retail | 1993 |
| Turku Food & Wine Fest Oy | Arts & recreation | 2017 |
| Turku Homes Oy | Real estate | 1991 |
| Turku Industries Oy | Manufacturing | 2014 |
| Turku International Oy Ltd | Professional & scientific | 2015 |
| Turku Invest Oy | Financial services | 2011 |
| Turku Kodit Oy | Construction | 2020 |
| Turku Marine Industry Holding Oy | Professional & scientific | 2013 |
| Turku Safety Oy | Education | 2022 |
| Turku Sixback Oy | Hospitality | 1992 |
| Turku Steel Oy | Manufacturing | 1993 |
| Turku Stevedoring Oy | Transport & logistics | 1998 |
| Turku Styling Systems Oy | Wholesale & retail | 1999 |
| Turku Taksi Palvelu Oy | Transport & logistics | 2024 |
| Turku Tool Management Oy | Financial services | 1995 |
| Turku Truck Center Oy | Other services | 2024 |
| Turku Type Industries Oy | Professional & scientific | 2014 |
| Turku Voima Oy | Construction | 2022 |
| Turku-Speed Consulting Ky | Professional & scientific | 1994 |
| Turku.cap Oy | Transport & logistics | 2025 |
| TurkuFight Oy | Arts & recreation | 2024 |
| TurkuVet Oy | Professional & scientific | 2021 |
| Turkubus Oy | Transport & logistics | 2012 |
| Turkuestradi Oy | Wholesale & retail | 1989 |
| Turkuhallin Palvelu Oy | Hospitality | 1998 |
| Turkulaine Reklaamifabriikki Oy | Professional & scientific | 2009 |
| Turkutailor Oy | Wholesale & retail | 2012 |
| Turo Trust Co. Oy | Financial services | 2007 |
| Turpeli Oy | Administrative & support | 2017 |
| Tursi Oy | Hospitality | 2019 |
| Turskatehdas Oy | Financial services | 2020 |
| Turun Ainova Osuuskunta | Arts & recreation | 2015 |
| Turun Airo Oy | Financial services | 2015 |
| Turun Allergiaklinikka Oy | Health & social care | 2008 |
| Turun Alueen Toimitilat Oy | Real estate | 2020 |
| Turun Aluekaivuu Oy | Construction | 1987 |
| Turun Aluekierrätys Oy | Construction | 1990 |
| Turun Apurit Oy | Transport & logistics | 2025 |
| Turun Arboristi- ja Viherpalvelu Oy | Administrative & support | 2026 |
| Turun Asuntoliike Oy | Real estate | 2020 |
| Turun Asuntomeklarit Oy LKV | Real estate | 2001 |
| Turun Asuntomyynti Oy | Real estate | 2012 |
| Turun Asuntosaneeraus Oy | Construction | 2002 |
| Turun Asuntoverkkokauppa Oy | Real estate | 2024 |
| Turun Auto-Center Oy | Wholesale & retail | 2008 |
| Turun Autohuolto Oy | Other services | 2010 |
| Turun Autolasi Oy | Other services | 2013 |
| Turun Autotyö Oy | Other services | 1981 |