| KarttaKomppania Oy | Information & communication | 2024 |
| KasaKon Oy | Construction | 2023 |
| Kasausmestarit Oy | Construction | 2026 |
| Kasetek Oy | Construction | 1998 |
| Kasikaivu Oy | Construction | 2024 |
| Kaski Metsät Oy | Agriculture & fishing | 2025 |
| Kaski Partners Oy | Manufacturing | 2014 |
| Kaskipuu Holding Oy | Financial services | 2015 |
| Kassanom Oy | Wholesale & retail | 2015 |
| Kassapolar Oy | Administrative & support | 2011 |
| Kassisen Asianajotoimisto Oy | Professional & scientific | 2017 |
| Kastelli Group Oy | Construction | 2017 |
| Kastelli-talot Oy | Construction | 2017 |
| Kastellin Erikoislääkäripalvelu Oy | Health & social care | 2010 |
| Kastellin Kiekkomedia avoin yhtiö | Professional & scientific | 2017 |
| Kastellin rakennus- ja kiinteistöpalvelu Oy | Real estate | 1993 |
| Kasvishovi Oy | Wholesale & retail | 1987 |
| Kasvubuukkaus Oy | Wholesale & retail | 2025 |
| Kasvukoski Oy | Real estate | 2020 |
| Kasvuluoto Oy | Professional & scientific | 2024 |
| Kasvun Luotsi Oy | Health & social care | 2020 |
| Kasvuvara Oy | Financial services | 2017 |
| KatRa Oy | Real estate | 2020 |
| Katarauna Consulting Oy | Professional & scientific | 1987 |
| Katariinan Vilske Oy | Health & social care | 2015 |
| Katermax Oy | Construction | 1994 |
| Kati Hiekkapelto Oy | Arts & recreation | 2013 |
| Katiusa Oy | Hospitality | 2008 |
| Katman Oy | Construction | 2003 |
| Katri Antell Oy | Professional & scientific | 1949 |
| Katsastusmestarit Oy | Professional & scientific | 2020 |
| Katsos Oy | Health & social care | 2019 |
| Katterla Oy | Construction | 1992 |
| Kattilarinne Oy | Real estate | 2025 |
| Katto-Kaasinen Oy | Construction | 2021 |
| Kauneushoitola Feeling It Oy | Other services | 2025 |
| Kauneushoitola Ihanainen Oy | Other services | 2019 |
| Kauneushoitola Uusi Kirsikka Oy | Other services | 2019 |
| Kauneuskeskus Lumikki Oy | Other services | 2013 |
| Kauneussalonki Oulu Oy | Other services | 2016 |
| Kaunis Koti Wilhelmiina Oy | Wholesale & retail | 2003 |
| Kaupinsähkö Oy | Construction | 2010 |
| Kauppahuone Eurovälitys Oy | Real estate | 1991 |
| Kauppatalo Kahdeksan Ky | Real estate | 2000 |
| Kauppatorin Kahvilamakasiinit Oy | Hospitality | 1998 |
| Kauppuri 5 Oy | Hospitality | 2010 |
| Kauppurien Kiinteistöt Oy | Real estate | 2016 |
| Kauppurin Lounas Oy | Hospitality | 2024 |
| Kavara Oy | Construction | 2018 |
| Keefas Oy | Construction | 2021 |
| Keesing Suomi Oy | Information & communication | 2022 |
| Kehitysaura Oy | Professional & scientific | 1997 |
| Kehitysinsinöörit Ky | Information & communication | 1983 |
| Kehityspartner Pirjo Haikola Ky | Education | 1998 |
| Kehontuntemus Ukkola Oy | Education | 2012 |
| Kehusmaat Oy | Transport & logistics | 2019 |
| Keihäs Group Oy | Construction | 2023 |
| Keijo Siikaluoma Oy | Health & social care | 1994 |
| Keikka Group Oy | Administrative & support | 2024 |
| Keisala Group Oy | Financial services | 2018 |
| Keko geopolymeerit Oy | Manufacturing | 2011 |
| Kellari Private Room Oy | Hospitality | 2025 |
| Kellonmeren Kala Oy | Agriculture & fishing | 2021 |
| Kelona Oy | Manufacturing | 2025 |
| Kelot Oy | Professional & scientific | 2021 |
| Kelvix Oy | Administrative & support | 2026 |
| Kemi Football Oy | Wholesale & retail | 2019 |
| Kemikalio Red Lips Ky | Wholesale & retail | 1999 |
| Kemin Vesi-Piste Oy | Construction | 1985 |
| Kempeleen AKK-Hallinnointi Oy | Real estate | 1992 |
| Kempeleen Linnanportti Oy | Real estate | 2023 |
| Kemple Oy | Hospitality | 1986 |
| Kenete Group Oy | Construction | 2016 |
| Kenkä-Markus Ky | Wholesale & retail | 1984 |
| Keret Software Oy | Information & communication | 2017 |
| Kerma Clothing Company Oy | Wholesale & retail | 2020 |
| Kero Digital Oy | Information & communication | 2024 |
| Kerstax Oy | Health & social care | 2019 |
| Keskinäinen Kiinteistö Oy Messi | Real estate | 1983 |
| Kesälasi oy | Construction | 2006 |
| Ketopojat Oy | Transport & logistics | 1983 |
| Ketterä Kaarlo Oy | Professional & scientific | 2023 |
| Kettuan Oy | Financial services | 2026 |
| Kevisco Estate Oy | Real estate | 2026 |
| Key Business Insights Oy | Professional & scientific | 2020 |
| KeyColleague Oy | Professional & scientific | 2011 |
| Keyloop (Finland) Holding Oy | Professional & scientific | 2009 |
| Keyloop (Finland) Oy | Information & communication | 2004 |
| Keysight Technologies Finland Oy | Manufacturing | 1986 |
| KiBe Oy | Manufacturing | 1993 |
| Kia Suni Oy | Arts & recreation | 2025 |
| Kiantum Technologies Oy | Professional & scientific | 2016 |
| Kickoff Oy | Financial services | 1999 |
| Kide Arkkitehdit Oy | Professional & scientific | 2023 |
| Kieliloikka Oy | Health & social care | 2024 |
| Kielo Growth Oy | Financial services | 2015 |
| Kiem Oy | Hospitality | 2014 |
| Kiertokaari Oy | Water & waste | 2014 |
| Kietka Oy | Health & social care | 2006 |
| Kiimingin Autofiksaamo Oy | Other services | 2019 |