| Irop Oy | Financial services | 1997 |
| Isot kengät Oy | Wholesale & retail | 2024 |
| J&J Back Ab | Real estate | 2025 |
| J.F. Back Capital Ab | Financial services | 2024 |
| JD Meta Oy | Administrative & support | 2025 |
| JHE Holding Oy | Financial services | 2019 |
| JK Masters Oy | Professional & scientific | 1997 |
| JKS Invest Oy | Financial services | 2021 |
| JV Kiiltokorjaus Oy | Real estate | 1994 |
| Jartor Oy | Wholesale & retail | 2020 |
| Jeta-Palvelu Oy | Professional & scientific | 1994 |
| Jo Val Oy | Wholesale & retail | 2008 |
| Jobio Engineering Oy | Professional & scientific | 2014 |
| Jobio Group Oy | Professional & scientific | 2014 |
| Julte Oy | Professional & scientific | 2023 |
| Juntinmäki Oy | Real estate | 1986 |
| Jussin Laatoitus ja Maalaus Ky | Construction | 1987 |
| JustClean Oy | Administrative & support | 2026 |
| Järvijoki Holding Oy | Real estate | 2025 |
| K&V Installation Oy | Construction | 2021 |
| K.O. Products Oy | Wholesale & retail | 2021 |
| KKA Capital Oy | Financial services | 2020 |
| KL-Putki Oy | Construction | 2019 |
| KM1 AI Oy | Wholesale & retail | 2026 |
| KPM Huolto Oy | Administrative & support | 2018 |
| Kaappo-Kiinteistöt Oy | Real estate | 2015 |
| Kaarinan Karkaisutyöt Oy | Manufacturing | 1994 |
| Kaarinan Sähköpalvelu Oy | Construction | 1995 |
| Kaarinan TR-Työstö Oy | Manufacturing | 1989 |
| Kaarinan Tehoapu Oy | Administrative & support | 2025 |
| Kaikukallio Invest Oy | Financial services | 2021 |
| Kaikukallion Vesiosuuskunta | Water & waste | 2019 |
| Kaivinkoneyhtymä Hokkanen & Hokkanen | Construction | 1975 |
| Kalle Jukala Oy | Financial services | 2008 |
| Kallind Oy | Wholesale & retail | 2026 |
| Kalske Productions Oy | Arts & recreation | 2024 |
| Kandu Oy | Information & communication | 2007 |
| Kanerva Holding Oy | Financial services | 2022 |
| Karl-Magnus Spiik Oy | Education | 2021 |
| Karlex Oy | Professional & scientific | 2014 |
| Kasvui Oy | Professional & scientific | 2025 |
| Kattohaukat Oy | Construction | 2024 |
| Kepo-Palvelut Oy | Wholesale & retail | 2009 |
| KiekkoKingi Oy | Wholesale & retail | 2021 |
| Kiesa-Kiinteistöt Oy | Real estate | 2012 |
| Kiinteistö Navigare Oy | Real estate | 2010 |
| Kiinteistö Oy Aurakatu 12 | Real estate | 2021 |
| Kiinteistö Oy Fridheminkallio | Real estate | 1973 |
| Kiinteistö Oy Fridheminranta | Real estate | 1973 |
| Kiinteistö Oy Jousitie 6 | Real estate | 2019 |
| Kiinteistö Oy Kaarinan Piispankulma | Real estate | 2016 |
| Kiinteistö Oy Kaarinan Piispantontti | Real estate | 2019 |
| Kiinteistö Oy Kaivertajankatu 4 | Real estate | 1988 |
| Kiinteistö Oy Koivuniemi | Real estate | 2025 |
| Kiinteistö Oy Nekalan Houston | Real estate | 2021 |
| Kiinteistö Oy Ojakkalan SP-talo | Real estate | 1987 |
| Kiinteistö Oy Pöytyän Urheilupuistontie | Real estate | 2002 |
| Kiinteistö Oy Rälssintie 6 | Real estate | 2021 |
| Kiinteistö Oy Saton Tori | Real estate | 1966 |
| Kiinteistö Oy Turun Puistomäenkatu 46 | Real estate | 1984 |
| Kiinteistö Oy Vantaan Manaus | Real estate | 2023 |
| Kiinteistö- ja öljypoltinhuolto Juhani Kosonen Oy | Administrative & support | 2002 |
| Kiinteistökehitys Nurmi Oy | Real estate | 2022 |
| Kiinteistökehitys Turku Holding Oy | Real estate | 2026 |
| Kiipeilykeskus K2 Oy | Arts & recreation | 2020 |
| Kilosport Liikuntapalvelut Oy | Administrative & support | 2009 |
| Kilosport Oy | Arts & recreation | 1992 |
| Kirte Oy | Construction | 1991 |
| Kliini Group Oy | Administrative & support | 2024 |
| Kofin Oy | Construction | 2014 |
| Koneboss Oy | Wholesale & retail | 1973 |
| Korjaamopalvelu Ahokas Oy | Other services | 2010 |
| Korjaamopalvelu Danielsson Oy | Other services | 2021 |
| Kosara Oy | Construction | 1990 |
| Kosken Leipomo Cafe Oy | Manufacturing | 2020 |
| Kosken Leipomo Oy | Hospitality | 2021 |
| Kosken tt oy | Administrative & support | 2023 |
| Kosola Oy | Wholesale & retail | 2019 |
| Kristiina Mäkinen Oy | Health & social care | 2014 |
| Kuljetus J. Kaappola Ky | Transport & logistics | 2020 |
| Kuljetusliike Suvinen Oy | Transport & logistics | 1990 |
| Kulmapaja Oy | Agriculture & fishing | 2010 |
| Kurkinen & Stoor Oy | Financial services | 2008 |
| Kuusenlatva Oy | Real estate | 1977 |
| Kärjen Lämpö Oy | Administrative & support | 1974 |
| Laivu OY | Professional & scientific | 2007 |
| LS Academy Oy | Education | 2006 |
| LS Smart Solutions Ky | Professional & scientific | 2006 |
| LS-Electric Oy | Construction | 2013 |
| LTTP Hakala Oy | Health & social care | 2026 |
| LVI MiPar Oy | Construction | 2024 |
| LVI-suunnittelu- ja energiakatselmustoimisto Erkki Lappalainen Oy | Professional & scientific | 1995 |
| LVIS TurkuTiimi Oy | Construction | 2024 |
| Laatu-Dealerit oy | Wholesale & retail | 1990 |
| Lab4Work Oy | Administrative & support | 2021 |
| Lahtivuori & Paavoseppä Oy | Professional & scientific | 2020 |
| Lahtivuori Consulting Oy Ltd | Professional & scientific | 2015 |
| Laineenkare Productions Oy | Professional & scientific | 2022 |
| Lainisalo Defence Painting Oy | Construction | 2012 |
| Lakehills Cosmetics Oy | Other services | 2022 |