| Jarmo & Jarno Production KY | Arts & recreation | 2005 |
| Jasa Invest Oy | Professional & scientific | 2021 |
| Jawacon oy | Administrative & support | 2018 |
| Jeans store Hollywood Oy | Wholesale & retail | 1985 |
| Jemseri Oy | Manufacturing | 1989 |
| Jermo Oy | Administrative & support | 2019 |
| Jobcomhan Oy | Professional & scientific | 1995 |
| Johe&Pojat Oy | Wholesale & retail | 2022 |
| Joofan Oy | Administrative & support | 2013 |
| Jope kiinteistöt Oy | Real estate | 2023 |
| Jorma Leppänen Oy | Manufacturing | 1989 |
| Jorma Salvi Oy | Real estate | 1979 |
| Jouni capitals Oy | Financial services | 1993 |
| Journaali Oy | Information & communication | 1979 |
| Joy's Light Ky | Wholesale & retail | 1999 |
| Juha ja Tiina Vainio Oy | Wholesale & retail | 2003 |
| Juhlapalvelu Tullin Kaffe Oy | Hospitality | 2023 |
| Juhlatalo Fåfänga Paviliongi Oy | Real estate | 2024 |
| Juhlatilat Piccolo oy | Real estate | 2022 |
| Jukka Sarin Oy | Wholesale & retail | 1989 |
| Julia LK Oy | Professional & scientific | 2020 |
| Jussi-Bussi Ky | Administrative & support | 1989 |
| Jälkpolv Oy | Financial services | 2019 |
| KA Lehtinen Oy | Manufacturing | 2001 |
| KAJ Asennus Oy | Manufacturing | 2025 |
| KDL group Oy | Construction | 2017 |
| KG Kiinteistöt Oy | Real estate | 2020 |
| KH-Capital Oy | Financial services | 2016 |
| Kiox-Ta OY | Manufacturing | 2020 |
| KJ Tammelin Oy | Real estate | 1988 |
| KK Ruoka Oy | Wholesale & retail | 2017 |
| KLHM Group Oy | Professional & scientific | 2026 |
| KLK-terveys oy | Health & social care | 2016 |
| KML Consulting Oy | Professional & scientific | 2012 |
| KOE Holding Oy | Financial services | 2022 |
| KOJV-Holding Oy | Real estate | 2025 |
| Komplex Ky | Professional & scientific | 2020 |
| KOY Lounaisväylä 9 | Real estate | 2016 |
| KOY Metsätuomistontie 3 | Real estate | 2018 |
| KPP Rakennus OY | Construction | 2019 |
| KT-Works Oy | Manufacturing | 1980 |
| Kaakao Tuotanto avoin yhtiö | Arts & recreation | 2007 |
| Kaihdin Rauma Oy | Wholesale & retail | 1987 |
| Kaiku HR Oy | Administrative & support | 2013 |
| Kaiku Henkilöstöpalvelut Pori Oy | Administrative & support | 2016 |
| Kaiku Henkilöstöpalvelut Rauma Oy | Administrative & support | 2014 |
| Kaiku Rekrytointipalvelut Oy | Administrative & support | 2022 |
| Kaiku Siivouspalvelut Oy | Administrative & support | 2023 |
| Kaira Halli Oy | Real estate | 2026 |
| Kaisan Kuppila Oy | Hospitality | 2008 |
| Kaivuulouhinta P ja R Peltola Oy | Construction | 1989 |
| Kajava - Lahja ja käsityö Oy | Wholesale & retail | 2020 |
| Kaksi Kundia Oy | Hospitality | 2020 |
| Kalatorin Majatalo ja Hotelli Ky | Hospitality | 1987 |
| Kalli Investment Oy | Financial services | 2023 |
| Kallikajaskari Oy | Real estate | 1989 |
| Kalliola Consulting Oy | Professional & scientific | 2024 |
| Kaluste-Ruohonen Oy | Construction | 1995 |
| KalusteRäätälit OY | Construction | 2024 |
| Kanalinrannan TB-Huolto Ky | Wholesale & retail | 1990 |
| KaneliBurger Oy | Hospitality | 2004 |
| Kantonen-Yhtiöt oy | Transport & logistics | 2010 |
| Kapakkakaks Oy | Hospitality | 2025 |
| Kaplaaki Oy | Transport & logistics | 1994 |
| Kappeliluhdan kebab pizzeria Oy | Hospitality | 2021 |
| Karhuvalu Oy | Manufacturing | 2003 |
| Kari Kivilahti Oy | Manufacturing | 1993 |
| Karinaukean Autopaikoitus Oy | Real estate | 1976 |
| Karpalotien Autopaikoitus Oy | Real estate | 1976 |
| Kascons Oy | Professional & scientific | 2004 |
| Kaskø Oy | Financial services | 2022 |
| Kasti Group Oy | Hospitality | 2023 |
| Katon pesut ja maalaukset HTA Oy | Construction | 2025 |
| Kattmill Oy | Administrative & support | 2015 |
| Kauneus Aaren Ky | Wholesale & retail | 1982 |
| Kauneus Tsaaritar oy | Wholesale & retail | 2015 |
| Kauneushoitola Tähkä Ky | Other services | 1992 |
| Kauneushoitola Vanessa Ky | Other services | 2005 |
| Kaunis-Tuotteet Oy | Manufacturing | 2024 |
| Kaupinsalo Dental Oy | Health & social care | 2023 |
| Kauppapuutarha A. Ryynänen Ky | Agriculture & fishing | 1985 |
| Kauppi Leasing Oy | Administrative & support | 2021 |
| Kauppilanrannan kesävesiosuuskunta | Water & waste | 2004 |
| Kedonperä Enterprises Oy | Professional & scientific | 2025 |
| Kehora Ky | Arts & recreation | 1987 |
| Kekan pyöräpaja Oy | Other services | 2013 |
| Kekkeroos Oy | Administrative & support | 2021 |
| Kellri Oy | Financial services | 2023 |
| KerTom Oy | Other services | 2019 |
| Keski-Suomen Talomestarit Kommandiittiyhtiö Leo Mäenpää | Wholesale & retail | 1986 |
| Keskisen Saariston Vesiosuuskunta | Water & waste | 2005 |
| Keskusmestarit Oy | Manufacturing | 2001 |
| Kesän Kukka Oy | Other services | 2025 |
| Ketjurauma Oy | Professional & scientific | 1998 |
| Kiinteistö Oy Aaren 13 | Real estate | 2003 |
| Kiinteistö Oy Anundila | Real estate | 1989 |
| Kiinteistö Oy Eurajoenranta | Real estate | 1981 |
| Kiinteistö Oy FereCenter | Real estate | 2013 |
| Kiinteistö Oy Hakunin Kaksikko | Real estate | 1989 |
| Kiinteistö Oy Hakunintie | Real estate | 1983 |