| JSA-Invest Oy | Professional & scientific | 1993 |
| JT Sarpola Oy | Administrative & support | 2022 |
| JTT Holding Oy | Real estate | 2022 |
| JTT Power Oy | Construction | 2012 |
| JV-Timanttiporaus Oy | Construction | 2007 |
| JaMiPa Oy | Health & social care | 2009 |
| Janepa Oy | Professional & scientific | 1998 |
| Janin RemonttiApu Oy | Construction | 2022 |
| Jape-Tuote Tintex Oy | Wholesale & retail | 1997 |
| Jari Hintikka Oy | Construction | 1991 |
| Jauvia Asset Oy | Real estate | 2026 |
| JiiPee Tuotanto Oy | Construction | 2024 |
| Johanna Pietilä Oy | Administrative & support | 2016 |
| Joint Environmental Strategies JES Oy | Professional & scientific | 1995 |
| Joint Expert Systems JES Oy | Information & communication | 1990 |
| Joonas Lyytinen Oy | Financial services | 2025 |
| JorKe Ky | Construction | 1983 |
| Juhala Holdings Oy | Information & communication | 2018 |
| Jylhävaara Oy | Manufacturing | 2011 |
| Jyväs Car Oy | Other services | 2020 |
| Jyväs-Marine Oy | Wholesale & retail | 2002 |
| Jyväskylän Multimagia OY | Professional & scientific | 1996 |
| Jyväskylän Tili-Plus Oy | Education | 2017 |
| Jyväskylän Vuokratuote Oy | Real estate | 1997 |
| Jyväsprint Oy | Manufacturing | 1993 |
| Jyvässeudun Johtokartoitus Oy | Professional & scientific | 2005 |
| Jyvässeudun Paino Oy | Manufacturing | 1989 |
| Jääskelä Innovation Oy | Hospitality | 2011 |
| K & R Elevator Oy | Construction | 2016 |
| K-Kraft Oy | Construction | 2011 |
| K-S huoneistoremppa Oy | Construction | 2021 |
| Kiinteistö OY Sammalsoppi | Real estate | 2007 |
| KS Hyötyauto Oy | Wholesale & retail | 2019 |
| KS Sähkökeskus Ky | | 1987 |
| Kallio Consulting Oy | Information & communication | 2015 |
| Kamasaksa Oy | Wholesale & retail | 2012 |
| Kanavuoren Pienvarastot Oy | Real estate | 2009 |
| Karimatinvest Oy | Real estate | 2018 |
| Kartio Invest oy | Real estate | 2013 |
| Kattotyö Veljekset Pennanen Oy | Construction | 2003 |
| Kaukotieto Oy | Information & communication | 2025 |
| Kaveos Oy | Information & communication | 2018 |
| KaviSales Oy | Professional & scientific | 2021 |
| Keljon Konehuolto Oy | Wholesale & retail | 2019 |
| Kennel Evergrey's Avoin yhtiö | Other services | 2003 |
| Keski-Suomen Auto-ja Kolarikorjaamo Oy | Other services | 2022 |
| Keski-Suomen Laatukoti Oy | Construction | 2021 |
| Keski-Suomen Rakennus Veikko Oy | Construction | 2026 |
| Keski-Suomen Raksa Oy | Construction | 1989 |
| Keski-Suomen Taloushallinto Oy | Professional & scientific | 1996 |
| Keski-Suomen Tarkastustalo Oy | Professional & scientific | 2011 |
| Kesmex Oy | Manufacturing | 1993 |
| Kespet Kiinteistöt Oy | Real estate | 2021 |
| Kespet Oy | Wholesale & retail | 2021 |
| Kestokoti Oy | Real estate | 2025 |
| Kiinteistö Oy Best Ever | Real estate | 2021 |
| Kiinteistö Oy Itäpäijänteentie 55 | Real estate | 1992 |
| Kiinteistö Oy Kuusamon Pulkkajärvi | Agriculture & fishing | 1989 |
| Kiinteistö Oy Leenankartano | Real estate | 1989 |
| Kiinteistö Oy Levyrinne | Real estate | 2005 |
| Kiinteistö Oy Sammallahti | Real estate | 1995 |
| Kiinteistö Oy Seenintie 13 | Real estate | 1999 |
| Kiinteistö Oy Tallilantie 11 | Manufacturing | 1982 |
| Kiinteistö Oy Vaaja-Marine | Real estate | 2019 |
| Kiinteistö Oy Vaajakosken Kalarintie 7 | Real estate | 1996 |
| Kiinteistö Oy Vaajakumpu | Real estate | 1987 |
| Kiinteistöpalvelu Farox Oy | Administrative & support | 2009 |
| Kiinteistöyhtiö R&T Peitso Oy | Real estate | 2018 |
| Kirjapaino Ässä Oy | Manufacturing | 1993 |
| Kivea Oy | Professional & scientific | 2021 |
| Klaava Consulting Oy | Information & communication | 2023 |
| Kommandiittiyhtiö Arkko | Manufacturing | 1975 |
| Konemieli Oy | Professional & scientific | 2020 |
| Koodipirtti Oy | Information & communication | 2026 |
| Kotimaiset Energiat Oy | Energy | 1988 |
| Kukkumäen Autohuolto Ky | Other services | 1999 |
| Kuljetus Aarnikotkat Oy | Transport & logistics | 1995 |
| Kuljetus Markku Suonpää Oy | Real estate | 1995 |
| Kuljetus Peltosalmi Oy | Transport & logistics | 2016 |
| Kuljetus Raitanen Oy | Transport & logistics | 2025 |
| Kuljetus Team Vaajakoski Oy | Transport & logistics | 2014 |
| Kuljetusapu Finne Oy | Transport & logistics | 2020 |
| Kuljetusliike E. ja T. Peltonen Ky | Transport & logistics | 1992 |
| Kuntokeskus SuperFitness Oy | Arts & recreation | 2010 |
| Kurunmäki Holding Oy | Financial services | 2025 |
| Kuura Goods Oy | Professional & scientific | 2020 |
| LANZ Consulting Oy | Professional & scientific | 2024 |
| LVI Perälä Ky | Construction | 2014 |
| LVI ja Rakennus Sarika Oy | Construction | 2015 |
| LVI-asennus Leino Oy | Construction | 2020 |
| Lasse Holmstedt Oy | Information & communication | 2022 |
| Lataksi Oy | Transport & logistics | 1993 |
| Laukaan painotuote Oy | Manufacturing | 2021 |
| Laurinniemen Niittylä Oy | Real estate | 1993 |
| Leo Leikman Ky | Transport & logistics | 1991 |
| Lightmotion Oy | Manufacturing | 2024 |
| Liikeinvest Oy | Real estate | 1981 |
| Lintuperspektiivi Oy | Administrative & support | 2021 |
| Lombacco Oy | Financial services | 2010 |
| Luftman Oy | Construction | 2019 |