| Koura Capital Oy | Financial services | 2021 |
| KouvoRakentajat Oy | Construction | 2019 |
| Kouvokate Oy | Construction | 1996 |
| Kouvola Cargo Handling Oy | Transport & logistics | 2003 |
| Kouvola Innovation Oy | Financial services | 2008 |
| Kouvola Red Fame Ky | Wholesale & retail | 2003 |
| Kouvolan Ajokoulutuskeskus Oy | Education | 1994 |
| Kouvolan Ammattiopisto Oy | Education | 2021 |
| Kouvolan Asennuspalvelu Oy | Construction | 2023 |
| Kouvolan Asunnot Oy | Real estate | 1982 |
| Kouvolan Autokiilto Lux Oy | Other services | 2016 |
| Kouvolan Autolasi Oy | Construction | 1996 |
| Kouvolan Automaalaamo Oy | Other services | 2001 |
| Kouvolan Automaalit T. Keränen Oy | Wholesale & retail | 1992 |
| Kouvolan Autosähkö Oy | Other services | 1976 |
| Kouvolan Brodeeraamo Oy | Manufacturing | 2017 |
| Kouvolan ETI-Power Oy | Education | 1995 |
| Kouvolan Elektroniikkapörssi Oy | Real estate | 1990 |
| Kouvolan Fysio-Center Ky | Health & social care | 1992 |
| Kouvolan Fysiotraining Oy | Health & social care | 2011 |
| Kouvolan Golf 24 Oy | Arts & recreation | 2025 |
| Kouvolan Grilli-Kipsa Oy | Hospitality | 2013 |
| Kouvolan Grillit Oy | Hospitality | 2011 |
| Kouvolan Hammasasema Oy | Manufacturing | 1978 |
| Kouvolan Hansan Kauppakäytävä Oy | Administrative & support | 2001 |
| Kouvolan Hansapysäköinti Oy | Transport & logistics | 1999 |
| Kouvolan Helmi Ky | Hospitality | 2026 |
| Kouvolan Henkilöstöpalvelut Oy | Administrative & support | 2021 |
| Kouvolan Hevosklinikka Oy | Professional & scientific | 2024 |
| Kouvolan Isännöintikolmio Oy | Real estate | 2009 |
| Kouvolan Kaihdin Shop Ky | Manufacturing | 2001 |
| Kouvolan Kaiverrus Ky | Manufacturing | 1987 |
| Kouvolan Kauppakerho Oy | Professional & scientific | 1947 |
| Kouvolan Kehys ja Taide Ky | Wholesale & retail | 1989 |
| Kouvolan Kiinteistömaalaus Oy | Construction | 1996 |
| Kouvolan Kiinteistöpuhdistus Kommandiittiyhtiö | Real estate | 1987 |
| Kouvolan Kiinteistötiimi Oy | Real estate | 2019 |
| Kouvolan Kiropraktiikka Oy | Health & social care | 2019 |
| Kouvolan Kone- ja Rakenneasennus Oy | Construction | 1985 |
| Kouvolan Konetikki Oy | Wholesale & retail | 1989 |
| Kouvolan Konttorihuolto Ky | Wholesale & retail | 1963 |
| Kouvolan Kotikeskus Oy | Real estate | 1988 |
| Kouvolan Kuivajää Oy | Wholesale & retail | 2014 |
| Kouvolan Laatulasi Oy | Construction | 1990 |
| Kouvolan Laatutarkastus Oy | Professional & scientific | 2021 |
| Kouvolan Laatutiimi Oy | Administrative & support | 2019 |
| Kouvolan Lakritsi Oy | Wholesale & retail | 1993 |
| Kouvolan Lukko Oy | Wholesale & retail | 1976 |
| Kouvolan Luontaistuote Oy | Wholesale & retail | 1987 |
| Kouvolan Lääketutko Oy | Professional & scientific | 2012 |
| Kouvolan Löytötavarapalvelu Oy | Administrative & support | 2011 |
| Kouvolan Matkatoimisto Oy | Administrative & support | 1986 |
| Kouvolan Mekasähkö Oy | Construction | 1992 |
| Kouvolan Mixam Oy | Wholesale & retail | 1997 |
| Kouvolan Monitoimi avoin yhtiö | Wholesale & retail | 1999 |
| Kouvolan Monitoimipalvelu Oy | Administrative & support | 2023 |
| Kouvolan Moottoriosakeskus Oy | Wholesale & retail | 1966 |
| Kouvolan Musiikki Oy | Wholesale & retail | 2001 |
| Kouvolan Palvelukiinteistöt Oy | Real estate | 2020 |
| Kouvolan Peltityö Oy | Construction | 1969 |
| Kouvolan Pesula Ky | Other services | 1973 |
| Kouvolan Pienmoottori kommandiittiyhtiö | Other services | 2008 |
| Kouvolan Pullakuskit Oy | Transport & logistics | 1993 |
| Kouvolan Putkityö Oy | Construction | 1993 |
| Kouvolan Rautatie- ja Aikuiskoulutus Oy | Education | 2014 |
| Kouvolan Rengaspalvelu Oy | Wholesale & retail | 1985 |
| Kouvolan Romumetallit Ky | Water & waste | 2019 |
| Kouvolan SF-Auto Ky | Wholesale & retail | 1989 |
| Kouvolan Saha Oy | Manufacturing | 1916 |
| Kouvolan Silmälasimarket Oy | Wholesale & retail | 2015 |
| Kouvolan Talohuolto Oy | Administrative & support | 2013 |
| Kouvolan Talopalvelu Oy | Administrative & support | 2023 |
| Kouvolan Tavarataksit Oy | Transport & logistics | 1992 |
| Kouvolan Teatteri Oy | Arts & recreation | 2008 |
| Kouvolan Teatteripalvelu Oy | Hospitality | 2025 |
| Kouvolan Tennishalli Oy | Arts & recreation | 1987 |
| Kouvolan Teollisuusasennus Oy | Manufacturing | 1986 |
| Kouvolan Teräsmies Oy | Wholesale & retail | 2017 |
| Kouvolan Tilausauto Oy | Real estate | 1959 |
| Kouvolan Truck Service Oy | Other services | 2004 |
| Kouvolan Tuutulakoti Oy | Health & social care | 2021 |
| Kouvolan Utinkatu 14 Oy | Real estate | 2019 |
| Kouvolan Valinta-Palvelu Askolin Kommandiittiyhtiö | Wholesale & retail | 1979 |
| Kouvolan Valohuone Oy | Wholesale & retail | 2011 |
| Kouvolan Vaunu Paajanen Oy | Wholesale & retail | 2014 |
| Kouvolan Verho Salonki Ky | Wholesale & retail | 1993 |
| Kouvolan Yritystilat Oy | Real estate | 2011 |
| Kouvolan eristys ja pelti Oy | Construction | 2017 |
| Kouvolan piha- ja talohuolto Oy | Administrative & support | 2023 |
| Kouvot Basket Oy | Arts & recreation | 2021 |
| Kovi Oy | Manufacturing | 1994 |
| Krismak Oy | Administrative & support | 2025 |
| Kukkakauppa Kehäkukka Oy | Wholesale & retail | 2025 |
| Kukkatalo Rosarium Oy | Wholesale & retail | 1985 |
| Kuljettava Oy | Transport & logistics | 2023 |
| Kuljetus A. Kataja Oy | Water & waste | 1988 |
| Kuljetus A. Parviainen Oy | Transport & logistics | 1981 |
| Kuljetus Akkanen Oy | Transport & logistics | 2009 |
| Kuljetus Ilkka Saukkonen Oy | Transport & logistics | 2014 |
| Kuljetus JetRe Oy | Construction | 1996 |