| Joel Honkanen Ky | | 1982 |
| Joensuun Talousohjaus Oy | Professional & scientific | 1987 |
| Johtokadun Auto Oy | Other services | 2007 |
| Joketuotanto Ky | Arts & recreation | 1989 |
| Jollan Oy | Professional & scientific | 2016 |
| Jormanni Oy | Construction | 2000 |
| Josen Saggese Oy | Financial services | 2026 |
| Journey Mappers Group Oy | Professional & scientific | 2020 |
| JuSe's Oy | Hospitality | 2025 |
| Juha Kankkunen Driving Academy Oy | Education | 1997 |
| Juha Riepponen Oy | Financial services | 2026 |
| Juhan Asennus Ky | Construction | 2005 |
| Juhmik Oy | Professional & scientific | 2020 |
| Jukka Puikkonen Oy | Wholesale & retail | 2013 |
| Jukurit HC Oy | Arts & recreation | 2009 |
| Juurela Invest Oy | Professional & scientific | 2021 |
| Juvan Hippu Oy | Financial services | 1988 |
| Juvosen Valinta Ky | Wholesale & retail | 2025 |
| JyLe Oy | Administrative & support | 2020 |
| Jyri & Laura Paasonen Oy | Professional & scientific | 2017 |
| Järvi-Suomen Aurinko Oy | Energy | 2022 |
| Järvi-Suomen Auto Ky | Education | 2003 |
| Järvi-Suomen Energia Oy | Energy | 1994 |
| Järvi-Suomen Kiinteistökonsultit Oy | Professional & scientific | 1993 |
| Järvi-Suomen Taloustiimi osuuskunta | Professional & scientific | 2000 |
| Järvi-Suomen Tili ja Isännöinti Ky | Real estate | 2007 |
| Järvi-Suomen Tuuli Oy | Energy | 2022 |
| Järvi-Suomen Valokuitu Oy | Information & communication | 2023 |
| Järvi-Suomen Vesi Oy | Water & waste | 1994 |
| Järvisuomen Sähkö Ky | Construction | 1989 |
| K Seppänen Ky | Construction | 1997 |
| K Simola Oy | Professional & scientific | 2002 |
| K&K Living Oy | Real estate | 2023 |
| K&S Heikinheimo Oy | Wholesale & retail | 2013 |
| K.Oy Wanha Länsmanni | Real estate | 2019 |
| K.Räihän Kirjakauppa Ky | Wholesale & retail | 1909 |
| K2-Sijoituspalvelut Oy | Financial services | 2009 |
| KH-Tarvike Oy | Construction | 1987 |
| KK-works oy | Other services | 2024 |
| KL-Ratkaisut Oy | Professional & scientific | 2014 |
| KMK-Tuotteet Oy | Manufacturing | 2024 |
| KN-Muuraus Kari Nykänen Ky | Construction | 2018 |
| KSM Myynti Oy | Financial services | 2014 |
| KTC-Tekniikka Oy | Construction | 1985 |
| KTR Timber Oy | Wholesale & retail | 2025 |
| KaTaLaKo Oy | Education | 2018 |
| Kaakkois-Suomen Ammattikorkeakoulu Oy | Education | 2012 |
| Kaakon Laatueristys Oy | Construction | 2016 |
| Kaarakyyti Oy | Transport & logistics | 2022 |
| Kaarirakennus Oy | Construction | 2009 |
| Kaarna Services Group Oy | Information & communication | 2018 |
| Kahio Oy | Information & communication | 2011 |
| Kahvila Nanda Oy | Hospitality | 2019 |
| Kaike Oy | Professional & scientific | 2023 |
| Kaikki Kotona Oy | Real estate | 2016 |
| Kaisu Jouha Oy Mikkeli | Health & social care | 2023 |
| Kaivola Capital Oy | Financial services | 2025 |
| Kakriainen Holding Oy | Construction | 2021 |
| KaksMarkka Oy | Real estate | 1991 |
| Kaksi Kapteenia Oy | Arts & recreation | 2018 |
| Kala-Kalle Ky Mikkeli | Wholesale & retail | 2000 |
| KalaVoltti Oy | Manufacturing | 2016 |
| Kalevankankaan Areena Oy | Arts & recreation | 2009 |
| Kalevankankaan Sijoitus Oy | Financial services | 1990 |
| Kallajärven vesiosuuskunta | Water & waste | 2005 |
| Kalliorinne Consulting Oy | Professional & scientific | 2001 |
| Kaluste Merka Ky | Manufacturing | 1990 |
| Kaluste-Mariella Ky | Manufacturing | 1989 |
| Kaluste-Repo Ky | Wholesale & retail | 1980 |
| Kantolan Rengas Oy | Wholesale & retail | 2005 |
| Karabulut Food Oy | Hospitality | 2025 |
| Karhuisa Oy | Professional & scientific | 2019 |
| Karhuntassu Oy | Wholesale & retail | 2006 |
| Kari Kovanen Oy | Transport & logistics | 1991 |
| Karikon Hinauspalvelu Oy | Transport & logistics | 2015 |
| Karin Multa ja Seulonta Ky | Mining & quarrying | 1988 |
| Karin Sähkö Ky | Construction | 1984 |
| KasiForest Oy | Agriculture & fishing | 2010 |
| KasvuEsedu Oy | Education | 2017 |
| Kasvutoimisto Kidea Oy | Professional & scientific | 2016 |
| Kasvuyritys Consulting & Invest Oy | Professional & scientific | 2014 |
| Katosta Lattiaan Oy | Construction | 2022 |
| Katri Skinnari Oy | Financial services | 2006 |
| Kattilanharju Oy | Real estate | 2017 |
| Kaukosäätö Mikkeli Oy | Construction | 2024 |
| Kauppahuone Harte Oy | Wholesale & retail | 1975 |
| Kedi avoin yhtiö | Hospitality | 1999 |
| Keeplio Oy | Information & communication | 2025 |
| Kelkkalan Puusepäntehdas Ky | Manufacturing | 1984 |
| Kelloliike V. Pylvänäinen Oy | Wholesale & retail | 1965 |
| Kemiallinen Pesula MIKEPE Oy | Other services | 2015 |
| Kemiallinen Pikapesula Quick Shop Oy | Other services | 1993 |
| Kenora Oy | Construction | 2018 |
| Kerienergia Oy | Energy | 1995 |
| Kerimäen Lämpö Oy | Energy | 1995 |
| Kermavaahtosuu Oy | Hospitality | 2015 |
| Keski-Savon Eristys Oy | Construction | 2011 |
| Keski-Suomen Automyynti Oy | Wholesale & retail | 2010 |
| Kestio OY | Other services | 2026 |
| Kidea IT Oy | Information & communication | 2022 |