| Hurukselan Vesihuolto-osuuskunta | Water & waste | 2008 |
| Huuma Kiinteistöt Oy | Real estate | 2021 |
| Huumantien kesäkahvila Oy | Hospitality | 2023 |
| Hydromax Oy | Manufacturing | 1992 |
| Hymypaikka Oy | Health & social care | 1997 |
| Hyvinvointikeskus Legacy OY | Arts & recreation | 2023 |
| Hyvinvoiva me oy | Arts & recreation | 2022 |
| Hyvä Isännöinti Kotka Oy | Real estate | 2012 |
| HyväWointi Oy | Health & social care | 2023 |
| Hyväntuulen Auto avoin yhtiö | Wholesale & retail | 1980 |
| Häkä Group Oy | Professional & scientific | 2022 |
| Häkäräiset Ky | | 1983 |
| Höyryhinaaja Ahkera Oy | Transport & logistics | 2018 |
| I-asennus Oy | Construction | 2020 |
| I-trader Kotka Oy | Wholesale & retail | 2013 |
| IE Coaching Oy | Professional & scientific | 2025 |
| IEI Services Oy | Construction | 2024 |
| IEL Ventures Oy | Professional & scientific | 2025 |
| IF-Saneeraus Oy | Construction | 2003 |
| Ikep OY | Real estate | 2022 |
| Ikivoima OY | Professional & scientific | 2019 |
| IL Partner Oy | Transport & logistics | 2022 |
| ILP-Tech oy | Construction | 2020 |
| INMARGO Oy | Transport & logistics | 2016 |
| IRi Valvonta Oy | Construction | 2023 |
| ISALJO Oy | Education | 2016 |
| IUI Talotekniikka Oy | Construction | 1993 |
| Ivmglobal Avoin Yhtiö | Wholesale & retail | 2005 |
| Ilma-Eero Oy | Construction | 2022 |
| Ilma-Osat Oy | Manufacturing | 1988 |
| Ilmakotka Ky | Construction | 1986 |
| Ilmari Kiinteistöt Oy | Hospitality | 2020 |
| Ilpower Oy | Other services | 2013 |
| InForge Oy | Information & communication | 2026 |
| Inch of Ink Oy | Professional & scientific | 2013 |
| IndServ H Oy | Manufacturing | 2025 |
| Indian Maharaja Grocery Store Oy | Hospitality | 2021 |
| Inkerikko Cargo Oy | Transport & logistics | 2012 |
| Inmartech Oy | Manufacturing | 2025 |
| Inncorpovation Oy | Professional & scientific | 2022 |
| Innocode Oy | Information & communication | 2018 |
| Innovator Finland Oy | Professional & scientific | 2025 |
| Insinööritoimisto Astecon Oy | Professional & scientific | 1994 |
| Insinööritoimisto Employ-Osakeyhtiö | Professional & scientific | 1979 |
| Insinööritoimisto H. Eskelinen Oy | Professional & scientific | 2009 |
| Insinööritoimisto JH-Suunnittelu Oy | Professional & scientific | 2012 |
| Insinööritoimisto JO-Kone Oy | Professional & scientific | 1988 |
| Insinööritoimisto Lasse Kilpinen Oy | Professional & scientific | 2007 |
| Insinööritoimisto Puolimatka Oy | Construction | 2009 |
| Insinööritoimisto RLN Oy | Manufacturing | 1988 |
| Insinööritoimisto Rakennussuunnittelu-ja Valvonta Valkoinen Linja Oy | Real estate | 2023 |
| Insinööritoimisto Ville Länsimies Oy | Professional & scientific | 2008 |
| Insurance House A & A OY | Financial services | 2015 |
| Inter Marine Oy | Manufacturing | 1993 |
| Inter Marine Service Oy | Manufacturing | 2010 |
| Intermodal Tank Transport Logistics UK Limited, sivuliike Suomessa | Transport & logistics | 2020 |
| Isopurje Oy | Transport & logistics | 2020 |
| Isännöinti Ankkuri Oy | Real estate | 2025 |
| Isännöintitoimisto Karhulan Talopalvelu Oy | Real estate | 2020 |
| Isännöitsijätoimisto Toivo Kaarmila Ky | | 1986 |
| Itärannan Sauna Oy | Other services | 2016 |
| J & J Lindström Oy | Transport & logistics | 1993 |
| J&J Protech avoin yhtiö | Administrative & support | 2016 |
| J. Hartikka Oy | Financial services | 1987 |
| JAM Capital Oy | Real estate | 2016 |
| JAS Yrityspolku Oy | Professional & scientific | 2025 |
| JEP. Eriksson Ky | Hospitality | 2008 |
| JEV-Kukka Oy | Wholesale & retail | 2015 |
| JH Konsultointi ja Varainhallintapalvelut Oy | Professional & scientific | 2024 |
| JH-Suunnittelu Oy | Professional & scientific | 2001 |
| JHOX Oy | Professional & scientific | 2025 |
| JIGTEX Oy | Wholesale & retail | 2018 |
| JIM Vesi- ja lämpöasennus Oy | Construction | 2005 |
| JKV Logistics Finland Oy | Construction | 2016 |
| JL Talotekniikka Oy | Construction | 2021 |
| JL Toimistopalvelut Oy | Professional & scientific | 2017 |
| JL-Rakenne Oy | Professional & scientific | 2016 |
| JM Hannus Oy | Hospitality | 2009 |
| JM Laiturit Avoin Yhtiö | Arts & recreation | 2016 |
| JMLink Oy | Professional & scientific | 2025 |
| JMRS Invest Oy | Real estate | 2011 |
| JP-Urakointi Ky | Construction | 1986 |
| JPH Talotekniikka Oy | Construction | 2018 |
| JPK Capital Oy | Financial services | 2026 |
| JPT Services Ky | Education | 1977 |
| JPT Works Oy | Construction | 2025 |
| JR Tarvekorjaamo & Logistics Oy | Other services | 2022 |
| JR Tarvekuljetus Oy | Transport & logistics | 2013 |
| JS Tili&Valmennus Oy | Professional & scientific | 2024 |
| JS-Tech Services Oy | Information & communication | 2026 |
| JSTL Yhtiö Oy | Other services | 2023 |
| JT Navis Oy | Transport & logistics | 2008 |
| JTSec Oy | Administrative & support | 2009 |
| JUVIJO Oy | Professional & scientific | 2017 |
| JV Rakennuskotka Ky | Construction | 2005 |
| JVS Serving Oy | Construction | 2019 |
| Jyltek OY | Real estate | 2024 |
| JaMi Remontointi Oy | Construction | 2025 |
| Jaakko Peltola Oy | Manufacturing | 2017 |
| JaakkoSan Oy | Administrative & support | 2022 |