| Busö Ab | Hospitality | 1993 |
| Bygg-Eliten Ab Oy | Construction | 2021 |
| Byggcenter Forsström Ab | Construction | 2015 |
| Byggdoktorn Ab | Construction | 2015 |
| Byggi Ab Oy | Construction | 2013 |
| Byggnads Ab, Rakennus Oy F Wickström | Construction | 2017 |
| Byggnads Kb Sören Wickström - Rakennus Ky Sören Wickström | Construction | 1982 |
| Byggnadsaffär Stefan Lindqvist Kb | Construction | 1979 |
| Byggnadsfirma R. Lindholm Kb | Construction | 1995 |
| Byggnadstjänst Kjell Holm Ab | Construction | 1994 |
| Bygotek Oy | Construction | 2017 |
| Bygotek Solutions Oy | Construction | 2026 |
| Bärholmsvägens vattenandelslag | Water & waste | 2019 |
| C-Fiber Hanko Oy | Information & communication | 2016 |
| C. Sundblom Byggplanering Ab Oy | Professional & scientific | 2024 |
| CEA Holding Oy | Financial services | 2014 |
| CF&S Finland Oy | Transport & logistics | 2017 |
| CJV-agenturaffär Kommanditbolag Jan Svartström | Real estate | 1973 |
| CODES digital media öppet bolag | Information & communication | 2012 |
| Cornerstone Selling Ky | Administrative & support | 2015 |
| Cafe Töölön Hemma avoin yhtiö | Hospitality | 2016 |
| Café Gamla Stan öppet bolag | Hospitality | 2020 |
| CalSarIT Oy | Professional & scientific | 2021 |
| CapAid Oy | Professional & scientific | 2025 |
| Caprico Trading Oy | Wholesale & retail | 1994 |
| Carl de Mumma Oy Ab | Hospitality | 2006 |
| Casi & co Oy Ab | Professional & scientific | 2021 |
| Chambon Oy | Wholesale & retail | 1992 |
| Chemiq Oy | Information & communication | 2025 |
| Choice Steel Oy | Wholesale & retail | 2007 |
| Chrispe-Invest Oy Ab | Real estate | 2000 |
| Clean-Kalle Ab Oy | Administrative & support | 1970 |
| Cleonari Music Ab Oy | Arts & recreation | 2023 |
| Cori Team Oy Ab | Professional & scientific | 1996 |
| CornerStone Siivous Palvelut Oy | Administrative & support | 2025 |
| Crea Event Oy Ab | Education | 2015 |
| Creo-Base Oy | Construction | 2011 |
| DS Fabrication Ab | Construction | 2022 |
| DaMi Invest Ab | Real estate | 2025 |
| Damex palvelut tjänster Oy Ab | Real estate | 2007 |
| Danskogin Saha Oy | Manufacturing | 2022 |
| Dee-Sijoitus Oy | Wholesale & retail | 1993 |
| Defmat Oy | Real estate | 1992 |
| Design of Success Öppet bolag | Information & communication | 2009 |
| Diesel-Korpela Oy-Ab | Other services | 1996 |
| Dimepal Oy Ab | Real estate | 1998 |
| Diploi Oy | Information & communication | 2024 |
| Djurhörnan Ab | Wholesale & retail | 2010 |
| Domax Oy | Information & communication | 1989 |
| Dot Point Oy | Other services | 2016 |
| Dovecon Ab Oy | Professional & scientific | 2013 |
| DriftNorth Ab | Professional & scientific | 2025 |
| E-Town Productions Ab | Arts & recreation | 2023 |
| Eelicom OY | Financial services | 2009 |
| EG-Trading Oy | Wholesale & retail | 2004 |
| EKM Service Ab Oy | Wholesale & retail | 1989 |
| EKSU - Ekenäs Stugservice & Uthyrning, Tammisaaren Mökkihuolto & Vuokraus Ab | Administrative & support | 2020 |
| ELMER Ab | Construction | 2007 |
| Elos Logistics OY | Transport & logistics | 2006 |
| Ehr El Ab Oy | Professional & scientific | 2023 |
| Eke-Haglund & Haglund Konsult Kb Ky | Wholesale & retail | 1989 |
| Eke-Vita Ab Oy | Real estate | 1994 |
| Ekehall Ab | Real estate | 2007 |
| Ekenäs Båtcenter Ab - Tammisaaren Venekeskus Oy | Wholesale & retail | 2024 |
| Ekenäs Båtvarv Ab | Manufacturing | 2011 |
| Ekenäs Camping Ab | Hospitality | 1999 |
| Ekenäs Entreprenad Ab | Transport & logistics | 1989 |
| Ekenäs Gästhamn Ab | Hospitality | 1992 |
| Ekenäs Hyrlift Kb-Ky | Administrative & support | 1999 |
| Ekenäs Idrottsförening Ab | Arts & recreation | 2014 |
| Ekenäs Maskintorg Kb-Ky | Other services | 1987 |
| Ekenäs Optik Eko Kb | Manufacturing | 1995 |
| Ekenäs Pr reklamtjänst Ab Oy | Professional & scientific | 1994 |
| Ekenäs Sparbank Ab | Financial services | 2020 |
| Ekenäs Tennishall Ab | Arts & recreation | 2001 |
| Ekenäs Trafikcenter Ab | Real estate | 1980 |
| Ekenäs Trävaruhus Ab | Wholesale & retail | 1999 |
| Ekenäs VVS-service, Tammisaaren LVI-huolto, öppet bolag | Construction | 1995 |
| Ekenäs Vulkanisering Eke-Vulk Kb Ky | Wholesale & retail | 1976 |
| Ekenäs bowling ab | Arts & recreation | 2002 |
| Ekepop Oy | Wholesale & retail | 2001 |
| Eklux Kb-Ky | Wholesale & retail | 1989 |
| Eklås Ab Tammilukko Oy | Wholesale & retail | 1981 |
| Ekonomax Öppet bolag - Avoin yhtiö | Professional & scientific | 2005 |
| Ekta Bryggeri Ab | Manufacturing | 2016 |
| Ekvall Planering och Konsultering Oy Ab (EPK) | Professional & scientific | 2023 |
| El-Marine Oy Ab | Construction | 2007 |
| Electronic Service Meba öppet bolag | Other services | 1986 |
| Elektro Marketing Oy Ab | Construction | 1995 |
| Element-Trans Winsten Oy Ab | Transport & logistics | 1992 |
| Elkonsulten Winberg Ab Oy | Professional & scientific | 2009 |
| Elonel Oy | Financial services | 1998 |
| Elplanering - Sähkösuunnittelu J. Björklund Ab | Professional & scientific | 2003 |
| Emmer Form Ab | Professional & scientific | 2020 |
| Endcore oy | Wholesale & retail | 2023 |
| Enetem Oy Ab | Financial services | 2024 |
| Erimin Oy | Professional & scientific | 1990 |
| Eristepalvelu S & T Oy Ab | Construction | 2020 |
| Espingskär Östergård Ab | Hospitality | 2022 |
| Estete Oy | Professional & scientific | 2006 |