| Nuorisokeskus Villa Elba Oy - Ungdomscentra Villa Elba Ab | Hospitality | 1991 |
| Nuutti Invest Oy | Financial services | 2025 |
| Nya Kem-Tvätt-Uusi Kem-Pesu om. Tauno ja Vuokko Markkanen | Other services | 1986 |
| Nénas omsorg Ab | Health & social care | 2025 |
| O. Salo Oy | Wholesale & retail | 1996 |
| OC Pohjanmaa Oy LKV | Real estate | 2024 |
| OK Company Oy | Administrative & support | 2024 |
| OM Happyplace Oy | Construction | 2008 |
| Onnen Kodit OY | Construction | 2013 |
| ORJT-Invest Oy | Real estate | 2008 |
| OSMA-Invest Oy | Financial services | 2015 |
| OV-Rakennus Ky | Real estate | 1985 |
| Ohjelmatoimisto V.Ullakko ky | Arts & recreation | 2002 |
| Ohraniemi Oy | Construction | 2024 |
| Oivalliset Oy | Administrative & support | 2022 |
| Olbia Oy | Financial services | 1993 |
| Olive Bay International Ky | Wholesale & retail | 2011 |
| Olli Vikström Oy | Financial services | 2011 |
| Olmaja Oy | Wholesale & retail | 1992 |
| Omnicap Oy | Professional & scientific | 1993 |
| Ompolina Oy | Professional & scientific | 1997 |
| Onnipirtti Oy | Arts & recreation | 1989 |
| Optimi Financing - Eurorahoitus Oy | Wholesale & retail | 1990 |
| Optivil Oy | Wholesale & retail | 2011 |
| Original Marmara Oy | Hospitality | 2023 |
| Original Trading Oy | Wholesale & retail | 2020 |
| Orvitex Oy | Wholesale & retail | 1994 |
| Ostrobothnian Yacht Service Oy | Manufacturing | 2009 |
| Osuuskauppa KPO | Wholesale & retail | 1912 |
| Osuuskunta Keskikaista | Information & communication | 2007 |
| Osuuskunta Naisten Talo Kokkolan resurssikeskus | Other services | 1995 |
| Osuuskunta Oivapäivä | Professional & scientific | 2015 |
| Osuuskunta Wintereich | Arts & recreation | 2007 |
| Osuvakoulutus Oy | Education | 2015 |
| Otakon Pohjanmaa Oy | Professional & scientific | 2021 |
| Ottomarino Oy | Construction | 2014 |
| Oulun Laatta-Asennus Oy | Construction | 2001 |
| Outi Airola Yxpila Media Oy | Professional & scientific | 2010 |
| Oveca Group Oy | Real estate | 2021 |
| Ovecon Oy | Professional & scientific | 2003 |
| Oy AE-Trading Ab | Professional & scientific | 1995 |
| Oy Adolf Lahti Yxpila Ab | Administrative & support | 2009 |
| Oy Ahlskog Ab | Manufacturing | 1945 |
| Oy Ahola Group Ab | Transport & logistics | 1978 |
| Oy Aspen Investment Ltd | Financial services | 2016 |
| Oy Autoliike Nystedt Bilaffär Ab | Wholesale & retail | 2009 |
| Oy Automyynti-Bilförsäljning L.Lerbacka Ab | Wholesale & retail | 1994 |
| Oy B Huhta Ab | Manufacturing | 1956 |
| Oy B&S Nordic Ab | Wholesale & retail | 1995 |
| Oy B. Björkstrand Ab | Construction | 1985 |
| Oy BWS-GROUP Ab | Construction | 2022 |
| Oy Birkegard Invest Ab | Financial services | 2017 |
| Oy Björkens Ab | Manufacturing | 2006 |
| Oy Brandt Fox Ab | Agriculture & fishing | 2011 |
| Oy Brandts Minkfarm Ab | Agriculture & fishing | 1976 |
| Oy Brandts Päls Ab | Real estate | 2002 |
| Oy Byggtjänst Sandvik Ab | Construction | 2018 |
| Oy Creamedia Invest Ab | Real estate | 2008 |
| Oy Danin Kelolattiat - Dans Torrfurugolv Ab | Manufacturing | 2005 |
| Oy E.A. Åström Ab | Real estate | 1977 |
| Oy Ecospec Ltd | Professional & scientific | 1991 |
| Oy Etsen Ab | Transport & logistics | 1994 |
| Oy FS-Svets Ab | Construction | 1989 |
| Oy Finespo Ab | Wholesale & retail | 1997 |
| Oy Forskor-Invest Ab | Financial services | 1986 |
| Oy Fristyle Ab | Professional & scientific | 2006 |
| Oy Furniture Consuls Ltd | Professional & scientific | 2001 |
| Oy GS-System Ab | Manufacturing | 1993 |
| Oy Galea Shipping Ab | Transport & logistics | 2010 |
| Oy H. Molander Ab | Transport & logistics | 1980 |
| Oy HK Trailer Invest Ab | Wholesale & retail | 2012 |
| Oy Haro-Invest Ab | Financial services | 1976 |
| Oy Hausa Ab | Professional & scientific | 2023 |
| Oy Hiltop Ab | Manufacturing | 2003 |
| Oy Hoh Ab | Real estate | 1991 |
| Oy Hänninen Engineering Ab | Professional & scientific | 2006 |
| Oy Intrading Ab | Wholesale & retail | 2014 |
| Oy K G Fagerholm Ab | Professional & scientific | 2010 |
| Oy Karisma Care Ab | Health & social care | 2022 |
| Oy Kew Ab | Professional & scientific | 2017 |
| Oy Kewatec AluBoat Ab | Manufacturing | 2005 |
| Oy Kokko-Bus Ab | Transport & logistics | 2013 |
| Oy Kokkolan Matkatoimisto - Karleby Resebyrå Ab | Administrative & support | 1984 |
| Oy Kokkolan Moottorihiomo Ab | Other services | 2005 |
| Oy Kokkolan Stemat | Construction | 1998 |
| Oy Kokkotel Service Ab | Wholesale & retail | 2006 |
| Oy Kone-Cocco Machine Ab | Wholesale & retail | 1999 |
| Oy Kotkamaa Ab | Professional & scientific | 2001 |
| Oy Kronobo Ab | Real estate | 2018 |
| Oy KustCar Kokkola Ab | Other services | 2010 |
| Oy Lahnakoski Ab | Manufacturing | 1971 |
| Oy Livohka | Real estate | 1979 |
| Oy M & V Brandt Ab | Manufacturing | 1996 |
| Oy M. Rauanheimo Ab | Transport & logistics | 1940 |
| Oy MICONE Group Ab | Manufacturing | 2019 |
| Oy Manister Ab | Real estate | 2014 |
| Oy Maple-House Ab | Manufacturing | 1971 |
| Oy Marmix | Real estate | 1988 |
| Oy MeCarLoS Ab | Construction | 2000 |
| Oy NBC Brewery Ab | Manufacturing | 2017 |