| A & S Toimistoasema Oy | Professional & scientific | 1992 |
| AH-Huolto Ky | Construction | 2010 |
| Abelita Oy | Professional & scientific | 2007 |
| Archipelago Ventures & Development Oy | Professional & scientific | 2024 |
| ArtTeatro avoin yhtiö | Arts & recreation | 2008 |
| Astrager Oy | Professional & scientific | 2018 |
| Avoin yhtiö Saariston Sieni | Agriculture & fishing | 1998 |
| Bestfish Oy Fin | Manufacturing | 2016 |
| Boaz Marketing Oy | Information & communication | 2017 |
| Competence Capital Oy | Education | 2000 |
| DT-Rakennus Oy | Construction | 2016 |
| Darma Oy | Professional & scientific | 2021 |
| Daviniki OY | Information & communication | 2018 |
| Dentipelago Oy | Real estate | 2026 |
| Engisholminniemen Vesiosuuskunta | Water & waste | 2012 |
| Fiume Invest Oy | Financial services | 2010 |
| GMCFinland Oy | Administrative & support | 2020 |
| Hauteri Oy | Agriculture & fishing | 1994 |
| Helsingin Laatu-Rapparit Oy | Construction | 2001 |
| Helsingin Tavarakuljetus Oy | Wholesale & retail | 2001 |
| Holiday Pleikilä Oy | Real estate | 2023 |
| Ilmasäätö Oy | Financial services | 1977 |
| Isle K Oy | Professional & scientific | 1995 |
| Istro Hyvinvointi Oy | Hospitality | 2010 |
| JYR-Cons Oy | Professional & scientific | 2005 |
| Jannen Lohi Oy | Agriculture & fishing | 1989 |
| KOSPE Oy | Agriculture & fishing | 2020 |
| KOy Lootholman Saaristokylä 1 | Real estate | 2014 |
| KOy Lootholman Saaristokylä 4 | Real estate | 2016 |
| Kaivonporaus Stenman Ky | Construction | 2002 |
| Kaivuu Lehtonen Oy | Construction | 2026 |
| Katanpään Linnake Oy | Hospitality | 2025 |
| Kihdin Loma, Lehtonen & Knit | Real estate | 1981 |
| Kiinteistö Oy Kustavin Konekeskus | Real estate | 1985 |
| Kiinteistöosakeyhtiö Itätalo Kustavi | Education | 1997 |
| Kiinteistöyhtiö Spauna Oy | Real estate | 2017 |
| Knaapi Holdings Oy | Real estate | 1988 |
| Korra Kalamatkat avoin yhtiö | Administrative & support | 1994 |
| Kuljetuspalvelu J. Siusluoto KY | Transport & logistics | 1986 |
| Kunnarainen Oy | Education | 2015 |
| Kustavi Marina Oy | Wholesale & retail | 2025 |
| Kustavin Agri OY | Agriculture & fishing | 2013 |
| Kustavin Asentajat Ky | Construction | 1990 |
| Kustavin Autokorjaamo Oy | Other services | 2015 |
| Kustavin Hirvirata Oy | Arts & recreation | 2010 |
| Kustavin Höyrysaha Oy | Manufacturing | 1931 |
| Kustavin Kalaranta Avoin yhtiö | Agriculture & fishing | 2007 |
| Kustavin Kalatehdas Oy | Agriculture & fishing | 2020 |
| Kustavin Kevon Lomakylä Oy | Hospitality | 2022 |
| Kustavin Laskenta Oy | Professional & scientific | 1985 |
| Kustavin Lämpö Oy | Energy | 2010 |
| Kustavin Marjaniemi Oy | Administrative & support | 2012 |
| Kustavin Matkailu Oy | Hospitality | 2009 |
| Kustavin Meritähti Ky | Wholesale & retail | 2004 |
| Kustavin Rakennusliike Oy | Construction | 1976 |
| Kustavin Rakennuspalvelu Engdahl Ky | Construction | 1985 |
| Kustavin Saaristosafari OY | Administrative & support | 2006 |
| Kustavin Savipaja Oy | Manufacturing | 1975 |
| Kustavin Sijoitus Oy | Real estate | 1990 |
| Kustavin Talouskauppa Ky | Wholesale & retail | 1961 |
| LT-Eriste Oy | Construction | 1994 |
| Laki- ja isännöintitoimisto Asko Lehtonen Oy | Professional & scientific | 1978 |
| Leton Lohi Ky | Agriculture & fishing | 1981 |
| Liikennetaito Ikola Ky | Education | 2010 |
| Likitalo Consulting Oy | Professional & scientific | 2021 |
| Lilas Oy | Hospitality | 2024 |
| Lypyrtin Kalasumput Ky | Agriculture & fishing | 1984 |
| Lännenpuolen Lohi Oy | Agriculture & fishing | 1983 |
| MAP Satamapalvelu Oy | Hospitality | 2010 |
| MOKKAPUU avoin yhtiö | Manufacturing | 2014 |
| MTH-Oy, Raisio | Construction | 2010 |
| Maistonki Ky | Manufacturing | 1995 |
| Medica & Medicus Oy | Health & social care | 2010 |
| Meiman-Valmennus Ky | Professional & scientific | 1991 |
| Merimaan vesi- ja jätevesiosuuskunta | Water & waste | 2007 |
| Merineule Oy | Manufacturing | 1983 |
| Munakarin Kala Ky | Agriculture & fishing | 1993 |
| Nermec Oy | Agriculture & fishing | 1994 |
| Niemisen kalastus Oy | Agriculture & fishing | 2012 |
| Nietek Oy | Construction | 2020 |
| O-PR Rakennus Oy | Construction | 2020 |
| Optimaari Oy | Wholesale & retail | 2001 |
| Orinkallio Oy | Real estate | 1990 |
| Oy Bonos Fructus Fennica Ab | Professional & scientific | 2009 |
| Oy Pureva Ab | Manufacturing | 1972 |
| Oy Saariston Jäädyttämö - Skärgårdens Fryseri Ab | Manufacturing | 1960 |
| Paratiisin Saalis Oy | Agriculture & fishing | 2020 |
| Paratiisipaja Oy | Manufacturing | 2021 |
| Paratiisipiha Ky | Manufacturing | 2003 |
| Peterzéns Oy | Wholesale & retail | 1982 |
| Pienkonekeskus Kiinteistöt Oy | Manufacturing | 2016 |
| Poonin Niemi Oy | Real estate | 1977 |
| Pro Pelago Oy | Professional & scientific | 2018 |
| Puistogolf ja Putiikki Oy | Arts & recreation | 2016 |
| Rahin Kala Oy | Agriculture & fishing | 2018 |
| Rahin Rakennus ja puutyö, Avoin yhtiö | Construction | 1999 |
| Rannikon HuoltoHomma Oy | Administrative & support | 2009 |
| Redlainer Oy | Administrative & support | 2021 |
| Remontti Alen Oy | Construction | 2022 |
| Riihimäki Yhtiöt Oy | Professional & scientific | 2015 |