| Koneurakointi M. Perälä Ky | Construction | 2013 |
| Koneurakointi Rusten Oy | Construction | 2025 |
| Koninklijke Luchtvaart Maatschappij N.V., sivukonttori Suomessa | Transport & logistics | 1980 |
| Konnex Oy | Construction | 2025 |
| Konsrax Oy | Information & communication | 2005 |
| Konstantinos Oy | Professional & scientific | 1989 |
| Konstiset Oy | Manufacturing | 1992 |
| Konsulentit Minttuja Oy | Administrative & support | 2007 |
| Konsultointi Kuusela Oy | Professional & scientific | 2020 |
| Konsultointi Ojala Oy | Professional & scientific | 1986 |
| Konsultointi Rano Oy | Professional & scientific | 2011 |
| Konsultoiva Kinnunen Oy | Professional & scientific | 2020 |
| Konsulttitoimisto Enersys Oy | Professional & scientific | 2000 |
| Konsulttitoimisto Niskanen & Pasanen Oy | Information & communication | 1991 |
| Konsura Oy | Professional & scientific | 2026 |
| Kontent Media Oy | Real estate | 2021 |
| Kontio Teho Oy | Professional & scientific | 2024 |
| Kontram Oy | Wholesale & retail | 1988 |
| Kontrol Konsultit Oy | Real estate | 2025 |
| Konttisuon Tuulivoima Oy | Energy | 2020 |
| Konttorikone V. Huolman Ky | Other services | 1963 |
| Konttorirotta Oy | Professional & scientific | 1994 |
| Kooamas Capital Oy | Financial services | 2017 |
| Koop Oy | Health & social care | 2014 |
| Koopari Oy | Real estate | 2015 |
| Koores Oy | Construction | 2021 |
| Kooshin S Taksi Oy | Transport & logistics | 2026 |
| Kopes Oy | Administrative & support | 1987 |
| Koponen Kodit Oy | Real estate | 2026 |
| Koppola Oy | Financial services | 2019 |
| Kore Metal Oy | Construction | 2020 |
| Korim Oy | Administrative & support | 2019 |
| Korjaamopalvelut Team Lahtinen Oy | Other services | 1998 |
| Korjaus KoJu Oy | Other services | 2025 |
| Korpela Capital Oy | Financial services | 2026 |
| Korrak Oy | Construction | 2025 |
| Korso 4 U Oy | Hospitality | 2025 |
| Korso Areena Oy | Arts & recreation | 2014 |
| Korso Invest Oy | Financial services | 2017 |
| Korso for you pizza Oy | Hospitality | 2026 |
| Korson Autohuolto Oy | Other services | 2015 |
| Korson Autopalvelu Ky | Other services | 1965 |
| Korson Autosepät Oy | Other services | 1993 |
| Korson Fysioterapia Ky | Health & social care | 1984 |
| Korson Hammas Avoin Yhtiö | Health & social care | 2004 |
| Korson Hius Club Oy | Other services | 1988 |
| Korson HiusSalonki Oy | Other services | 1984 |
| Korson Koti Lkv Juha Julin Oy | Real estate | 1995 |
| Korson Pesu Ky | Other services | 2006 |
| Korson Pizzapalvelu Sero Oy | Hospitality | 2014 |
| Korson Tasoite Oy | Construction | 2019 |
| Korson Vierumäen Huolto Oy | Energy | 1972 |
| Korson Zuhat oy | Hospitality | 2023 |
| Korsto-Palvelut Oy | Construction | 2017 |
| Kortteliravintelit Oy | Professional & scientific | 2019 |
| Korttilinna Oy | Wholesale & retail | 2010 |
| Korukaivos Oy | Wholesale & retail | 1995 |
| Kos-trans Oy | Transport & logistics | 2023 |
| Kosan Gas Finland Oy | Wholesale & retail | 2000 |
| Koskelin Holding Oy | Administrative & support | 2020 |
| Koskia Oy | Financial services | 2017 |
| Koskisen peltikate Oy | Manufacturing | 1982 |
| Kosmo Oy | Financial services | 1988 |
| Kostakki avoin yhtiö | Hospitality | 2015 |
| Kotamäki Group Oy | Professional & scientific | 2025 |
| Kote Oy | Construction | 2017 |
| Koti Kontto Oy | Financial services | 2008 |
| Koti Tarvitsee Siivous OY | Administrative & support | 2025 |
| Koti Vaihtoon LKV Oy | Real estate | 2021 |
| Koti- ja hoivapalvelut Sarilla Oy | Health & social care | 2017 |
| Koti- ja siivouspalvelu Raija Oy | Health & social care | 1986 |
| KotiLoiste Oy | Administrative & support | 2026 |
| Kotiapu Eimat Oy | Administrative & support | 2013 |
| Kotiapu SiTa Oy | Administrative & support | 2021 |
| Kotiforum Oy LKV | Real estate | 1994 |
| Kotihessut Oy | Real estate | 2024 |
| Kotihoito Lusi Oy | Health & social care | 2024 |
| Kotikolmoset Oy | Construction | 1998 |
| Kotilaisen kone Oy | Education | 2014 |
| Kotimaailma Group Oy | Professional & scientific | 2022 |
| Kotimajoitus Katariina Jäämeri-Lissapon Oy | Hospitality | 2009 |
| Kotinotko Oy | Construction | 2008 |
| Kotipalvelu Eve Oy | Health & social care | 2021 |
| Kotipalvelu Hopea Joutsen Oy | Health & social care | 2020 |
| Kotipalvelu/ Hemtjänst Wilma Oy | Health & social care | 2021 |
| Kotisi Energia Nordic Oy | Wholesale & retail | 2016 |
| Kotisihuolto Oy | Information & communication | 2021 |
| Kotiverkko Oy | Wholesale & retail | 1994 |
| Kotokunta Oy | Health & social care | 2016 |
| Kotoperhe Oy | Health & social care | 2026 |
| Kottis Media Oy | Professional & scientific | 2025 |
| Koukkupaja Oy | Wholesale & retail | 2009 |
| Kouluasuntola Kaupunkikoti Oy | Hospitality | 1999 |
| Koulutus Invest Oy | Education | 2016 |
| Koulutus- ja Konsultointikeskus Aitologia Oy | Education | 2014 |
| Koulutuskampa Oy | Education | 1976 |
| Koura & Kuljetus Asikainen Oy | Transport & logistics | 2022 |
| KoutZe Digital Oy | Information & communication | 2026 |
| Koutakorpi Oy | Real estate | 2013 |
| Koutakuru Oy | Real estate | 2011 |