| Jockey Oy | Arts & recreation | 1987 |
| Joenrinne Films Oy | Information & communication | 2021 |
| Jolilane Oy | Construction | 2012 |
| Jomi Invest Oy | Financial services | 1987 |
| Jonatron Oy | Wholesale & retail | 1993 |
| Jonrak-Myynti & Rakennus Oy | Construction | 1996 |
| Josla Oy | Education | 2010 |
| Juige Oy | Administrative & support | 2006 |
| Julie Sales Oy | Professional & scientific | 2023 |
| Junnikkala Invest Oy | Real estate | 2019 |
| Junnun Kuljetus Ky | Transport & logistics | 2017 |
| Jupcon Oy | Professional & scientific | 1990 |
| Jusmatics Oy | Professional & scientific | 1993 |
| Jussi Lehtonen Consulting JLC Oy | Administrative & support | 2006 |
| Juusela consulting oy | Financial services | 2019 |
| JököWee Oy | Construction | 1967 |
| K & N Rakennuspalvelu Ky | Professional & scientific | 2005 |
| KAIHO Elämyssauna Oy | Arts & recreation | 2026 |
| KB Auto Finland Oy | Wholesale & retail | 2019 |
| KH-Motors Oy | Other services | 1996 |
| KKV-Kiinteistöt Oy | Hospitality | 2017 |
| KL. SAVE Oy | Transport & logistics | 2020 |
| KMAC Sisäilmapalvelut Oy | Construction | 2022 |
| KPK-Service Oy | Transport & logistics | 2017 |
| KPS Promotion Oy | Arts & recreation | 2011 |
| KPT Työt Oy | Construction | 2022 |
| KT Kodin Tyyli Oy | Wholesale & retail | 2001 |
| KT Sales & Solutions Oy | Professional & scientific | 2013 |
| KTK Konetyö ja Kuljetus OY | Construction | 2023 |
| Kahvimaan Auto Oy | Other services | 1995 |
| Kajosan Oy Vihti | Administrative & support | 2026 |
| Kapasity Oy | Professional & scientific | 1989 |
| Karasjärvi Capital Oy | Professional & scientific | 2026 |
| Karax Ky | Administrative & support | 2008 |
| Karest Oy | Hospitality | 2018 |
| Karhu Crew Muuttopalvelut Oy | Transport & logistics | 2025 |
| Kari & Mira Productions Oy | Professional & scientific | 2024 |
| Karmican Oy | Real estate | 2021 |
| Kaskav Oy | Construction | 2023 |
| Kaski Solutions Oy | Information & communication | 2026 |
| Kasvivalo Online Oy | Wholesale & retail | 2015 |
| KellyMust Oy | Other services | 2026 |
| Kevytkenkä ky Heikki Vuorinen | Wholesale & retail | 1986 |
| Kiilanet Kommandiittiyhtiö | Manufacturing | 2001 |
| Kiiltäväx Oy | Administrative & support | 2021 |
| Kiinteistö Groma Oy | Construction | 1989 |
| Kiinteistö Oy Ajurinrinne | Real estate | 2008 |
| Kiinteistö Oy Ajurintie 2 | Real estate | 1990 |
| Kiinteistö Oy Ajurintie 8 | Real estate | 1990 |
| Kiinteistö Oy Hilpana | Real estate | 1991 |
| Kiinteistö Oy Juurakkotie 2 | Real estate | 2000 |
| Kiinteistö Oy Karkkilan Virastotalo | Real estate | 2011 |
| Kiinteistö Oy Kunnari | Real estate | 1991 |
| Kiinteistö Oy Lankila 11 | Real estate | 1976 |
| Kiinteistö Oy Lankilan Juuritie 6 | Real estate | 2015 |
| Kiinteistö Oy Nummelan Luontola | Real estate | 2002 |
| Kiinteistö Oy Nummelan Metsänreuna | Real estate | 2013 |
| Kiinteistö Oy Nummelan Muotola | Real estate | 2021 |
| Kiinteistö Oy Nummelan Mäihätie 16 | Real estate | 1989 |
| Kiinteistö Oy Nummelan Päivärinne | Real estate | 1988 |
| Kiinteistö Oy OP-Kaari | Real estate | 2001 |
| Kiinteistö Oy Peräsimentie 4 | Real estate | 1986 |
| Kiinteistö Oy Pettap | Real estate | 1994 |
| Kiinteistö Oy Prokätkä | Real estate | 2003 |
| Kiinteistö Oy Rakkatasku | Real estate | 2005 |
| Kiinteistö Oy Uunisaari | Real estate | 2015 |
| Kiinteistö Oy Vihdin Elokuja 5 | Real estate | 2001 |
| Kiinteistö Oy Vihdin Linnannokka | Real estate | 1996 |
| Kiinteistö Oy Vihdin Ratapelto | Real estate | 2010 |
| Kiinteistö Oy Vihdin Riihikorpi | Real estate | 1993 |
| Kiinteistö Zell Mosel Oy | Real estate | 2015 |
| Kiinteistö-Huiput Oy | Real estate | 2022 |
| Kiinteistöemännät Oy | Real estate | 2024 |
| Kiinteistöputki Oy | Construction | 2024 |
| Kiinteistötoimisto KK-Notariaatti Oy | Real estate | 1989 |
| Kikomi Oy | Professional & scientific | 2007 |
| Kinnula Invest Oy | Financial services | 2022 |
| Kirjanpito Kirsi Oy | Professional & scientific | 1992 |
| KiroCenter Oy ltd | Health & social care | 2004 |
| Kithorn Oy | Administrative & support | 1993 |
| Klassikkohallit Oy | Real estate | 2017 |
| Koivua Kotiin Oy | Wholesale & retail | 2024 |
| Koivuluoma Garage Oy | Other services | 2024 |
| Kojoottimatkat Oy | Administrative & support | 2020 |
| Kolikko-Mikko Oy | Arts & recreation | 1996 |
| Komu Pro Oy | Professional & scientific | 2026 |
| Kone-Huiput Oy | Wholesale & retail | 2024 |
| Kone-Hyvärinen Oy | Construction | 1983 |
| Konehuolto Säilä Oy | Other services | 2023 |
| Konekaksikko Ky | Wholesale & retail | 1984 |
| Konetyö Forsén Oy | Construction | 2016 |
| Koneurakointi Hynnälä Oy | Construction | 2011 |
| Koneurakointi S. Huotarinen Oy | Mining & quarrying | 2014 |
| Konsultointi ML Oy | Construction | 2017 |
| Konsulttitoimisto Kaaderi Oy | Information & communication | 2007 |
| Koodimaja Oy | Information & communication | 2022 |
| Koreaus Oy | Arts & recreation | 2023 |
| Korjaamokeisarit Oy | Other services | 2024 |
| Kosel Oy | Administrative & support | 2015 |
| Koski Construction Oy | Professional & scientific | 2013 |