| IAM Creative Capital Oy | Information & communication | 2025 |
| ICON Kiinteistökehitysrahasto Ky | Financial services | 2017 |
| ICON Real Estate Fund II - Syöttörahasto I Ky | Real estate | 2015 |
| ICON Real Estate Fund III - Suurpelto Ky | Financial services | 2014 |
| ICON Real Estate Fund IV - Kruunu Ky | Financial services | 2017 |
| ICON Real Estate Fund V - Ilves Ky | Financial services | 2017 |
| ILC Kiinteistöpalvelu Oy | Real estate | 2005 |
| IML Group Oy Ab | Wholesale & retail | 2004 |
| INS Construction Oy | Construction | 2026 |
| INTALO Oy | Professional & scientific | 2026 |
| INTERNOS Psykoterapiakeskus Oy | Health & social care | 2008 |
| IP-Label Finland Oy | Information & communication | 2007 |
| ITMax AB | Information & communication | 2018 |
| Ivory Beauty AB | Other services | 2022 |
| Idae Oy | Financial services | 2024 |
| Ideal Future Oy | Professional & scientific | 2006 |
| Ideasteel Company Oy | Manufacturing | 1999 |
| Iecon Oy | Construction | 1991 |
| Ifonetti Oy | Professional & scientific | 2007 |
| Iggy Agency Finland Oy | Professional & scientific | 2026 |
| Ihohud Vaasa Oy Ab | Health & social care | 1996 |
| Illyrian's Avoin Yhtiö | Hospitality | 2010 |
| Ilmastointiasennuspalvelu Timo Järvinen Ky | Construction | 2009 |
| Ilona Kuntoutus Oy | Health & social care | 2015 |
| Ilosen Leipomo Avoin Yhtiö | Manufacturing | 1968 |
| Img Media Ab Oy | Professional & scientific | 2011 |
| Immango Ab | Wholesale & retail | 2019 |
| Impi Consulting Oy | Professional & scientific | 2023 |
| Improve Research Oy | Professional & scientific | 2007 |
| InMedi oy | Health & social care | 2013 |
| Indevit Oy Ab | Information & communication | 2022 |
| Indevit Solutions Oy Ab | Information & communication | 2011 |
| Inedco Ab | Professional & scientific | 1990 |
| Infinity Investments Oy | Professional & scientific | 2024 |
| InflaClub Ab | Administrative & support | 2023 |
| Inforimi Oy | Wholesale & retail | 2005 |
| Infraview Oy | Professional & scientific | 2026 |
| Ingenjörsbyrå Mathias Smeds Ab Oy Insinööritoimisto | Professional & scientific | 1996 |
| Initium Novum Oy | Professional & scientific | 2026 |
| Injection & Glow Service Oy | Other services | 2010 |
| Innowo Consulting Oy | Professional & scientific | 2023 |
| Insane food lab Oy | Manufacturing | 2024 |
| Inselec Oy | Construction | 2022 |
| Inshomes Oy | Real estate | 2021 |
| Insinööripalvelut ToP Oy | Professional & scientific | 2024 |
| Insinööritoimisto - Ingenjörsbyrå A&P, Allan Andersson Ky Kb | Professional & scientific | 1985 |
| Insinööritoimisto A Hänninen Oy | Wholesale & retail | 1997 |
| Insinööritoimisto AlphaP Oy | Professional & scientific | 2020 |
| Insinööritoimisto Divacon Oy | Professional & scientific | 2017 |
| Insinööritoimisto Esatec Oy | Professional & scientific | 2000 |
| Insinööritoimisto Jakobsson Oy Ab | Professional & scientific | 2021 |
| Insinööritoimisto Luopajärvi Oy | Construction | 1990 |
| Insinööritoimisto Raimo Niskanen Oy | Real estate | 1991 |
| Insinööritoimisto Tepac Oy | Construction | 1993 |
| Instech Oy | Construction | 2017 |
| Intercity-Trans Oy | Real estate | 1988 |
| Intoart Oy Ab | Arts & recreation | 2011 |
| Intodata Oy | Information & communication | 2022 |
| Intrx Oy | Wholesale & retail | 2019 |
| Invataksi Niemi Oy | Transport & logistics | 2021 |
| Invataksi Seppälä Oy | Transport & logistics | 2020 |
| Invest Box Oy | Financial services | 1989 |
| Investia Ab | Financial services | 1996 |
| Investigo Oy Ab | Professional & scientific | 2015 |
| Investiris Oy | Financial services | 2025 |
| Investit Ab Oy | Real estate | 2025 |
| Ironfistmassage öppet bolag | Health & social care | 2017 |
| Isla Aduro Öppet bolag | Arts & recreation | 2011 |
| Isokangas service Oy | Wholesale & retail | 2019 |
| Isonkyrön Rantakiinteistöt Oy | Real estate | 1991 |
| Isännöinti Mäkinen Oy | Real estate | 1980 |
| Isännöintipalvelu Kilpi Oy | Real estate | 2003 |
| Isännöintipalvelut BS Oy | Real estate | 2014 |
| Isäntä Yhtiöt Oy | Financial services | 2024 |
| J Renko Oy | Hospitality | 2009 |
| J. Forss Oy/Ab | Wholesale & retail | 2008 |
| J. K. Järvi Oy | Financial services | 2023 |
| J. Keturi Oy | Wholesale & retail | 2005 |
| J. Kuoppala Ky | Transport & logistics | 1989 |
| J.E. Blåfield Oy | Construction | 1993 |
| J.Hyllinen Invest Oy | Financial services | 2013 |
| J.S. Taxi & Invest Oy | Transport & logistics | 2018 |
| J.S.C. Business Oy | Professional & scientific | 1990 |
| J2K Projects Oy | Arts & recreation | 2026 |
| Jabalm OY | Administrative & support | 2024 |
| JABB Consulting Oy Ab | Information & communication | 2012 |
| JASAP Oy | Professional & scientific | 2015 |
| JEA Invest Ab | Wholesale & retail | 1993 |
| JEMI Pro Oy Ab | Health & social care | 2021 |
| JETU RENT Oy | Arts & recreation | 2025 |
| JJL Yhtiöt Oy | Financial services | 2021 |
| JJM Österberg Invest Oy Ab | Financial services | 2023 |
| JJS Capital Oy | Financial services | 2020 |
| JKP Invest Oy | Financial services | 2026 |
| JKP-RenoInvest Oy | Real estate | 2024 |
| JL Core Oy | Professional & scientific | 2025 |
| JL Solutions Oy | Professional & scientific | 2012 |
| JLL Team avoin yhtiö | Hospitality | 2018 |
| JM-Care Oy | Real estate | 2021 |
| JMJ Capital Oy | Financial services | 2021 |