| Iisalmen Metsätoimisto Oy | Agriculture & fishing | 1992 |
| Iisalmen Nuohouspalvelu Oy | Administrative & support | 2008 |
| Iisalmen Olutmestari Oy | Hospitality | 2009 |
| Iisalmen Parturi Oy | Other services | 2025 |
| Iisalmen Pelti ja Ilmastointi Oy | Construction | 1996 |
| Iisalmen Pesupalvelu Ky | Other services | 1979 |
| Iisalmen Putkiasennus Oy | Construction | 1979 |
| Iisalmen RH-Yhtiöt Oy | Real estate | 2011 |
| Iisalmen Rahti Oy | Transport & logistics | 1999 |
| Iisalmen Rekkapiste Oy | Other services | 2019 |
| Iisalmen Sahat Oy | Manufacturing | 2008 |
| Iisalmen Sankar-Invest Oy | Financial services | 2002 |
| Iisalmen Sotekiinteistöt Oy | Real estate | 2025 |
| Iisalmen Suurtaloustekniikka Ky | Other services | 2011 |
| Iisalmen Sähkö ja Automaatio Oy | Construction | 2002 |
| Iisalmen Sähköpiste Oy | Construction | 2000 |
| Iisalmen Taksiliikenne Oy | Transport & logistics | 2011 |
| Iisalmen Tehoraivaus Ky | Agriculture & fishing | 1987 |
| Iisalmen Teollisuuskiinteistöt Oy | Real estate | 2012 |
| Iisalmen Teollisuuskylä Oy | Real estate | 1974 |
| Iisalmen Terveydenhoitotuote Oy | Wholesale & retail | 2022 |
| Iisalmen Teräpalvelu Oy | Manufacturing | 1984 |
| Iisalmen Teräs ja Romu Oy | Wholesale & retail | 2013 |
| Iisalmen Tilipalvelu Oy | Professional & scientific | 2019 |
| Iisalmen Tilitiimi Oy | Professional & scientific | 2015 |
| Iisalmen Torigrilli Ky | Hospitality | 1991 |
| Iisalmen Vaunu ja Sähköhuolto Oy | Construction | 1992 |
| Iisalmen Vesi ja Lämpö Oy | Construction | 1997 |
| Iisalmen Yrityskeskus Oy | Real estate | 1991 |
| Iisalmen Yritystalo Oy | Real estate | 1998 |
| Iisound Hirvonen & Kauppinen | Arts & recreation | 1990 |
| Iitek avoin yhtiö | Manufacturing | 1991 |
| Ikolanmäen Tila Oy | Agriculture & fishing | 2026 |
| Ilari Group Oy | Wholesale & retail | 2015 |
| Ilien Ky | Agriculture & fishing | 2018 |
| Ilmastointi Paananen Ky | Construction | 1954 |
| Impex ER Ltd Oy | Wholesale & retail | 1996 |
| Inora Oy | Manufacturing | 1993 |
| Insinööri Kiinteistöt Oy | Real estate | 2010 |
| Insinööritoimisto Hanico Oy | Professional & scientific | 2025 |
| Insinööritoimisto Savolainen Oy | Professional & scientific | 1975 |
| Insinööritoimisto Ylä-Savon Rakennussuunnittelu Oy | Professional & scientific | 1983 |
| Intertrade Rönkä ky | Wholesale & retail | 1988 |
| Ioni Oy | Information & communication | 2012 |
| Isännöintipalvelu Priima Oy | Transport & logistics | 2015 |
| Itä-Suomen Tulosviestintä Ky | Professional & scientific | 1997 |
| J & H Yhtymä Oy | Construction | 2003 |
| J Ripatti Ky | Construction | 1978 |
| J&S Kärkkäinen Oy | Transport & logistics | 2023 |
| J. & H. Katainen Ky | Wholesale & retail | 1982 |
| J. Väisänen Ky | Transport & logistics | 2011 |
| JAK-Invest Ky | Real estate | 2013 |
| Jarveco OY | Manufacturing | 2011 |
| JD Rakennus Oy | Construction | 2013 |
| JEA Ravintolat Oy | Hospitality | 2023 |
| JH-Finanssi Oy | Professional & scientific | 1981 |
| JJ Experts Oy | Manufacturing | 2026 |
| JJ Porovesi Oy | Information & communication | 2011 |
| JK Luistinhuolto Oy | Manufacturing | 2022 |
| JKA Group OY | Professional & scientific | 2024 |
| JM-Vuokraus Oy | Administrative & support | 2018 |
| JML Autohuolto Oy | Other services | 2014 |
| JSH Deals Oy | Wholesale & retail | 2016 |
| JT Pehkonen Oy | Manufacturing | 2024 |
| Jamo Investment Company Oy | Financial services | 2023 |
| JanaCaravan Oy | Wholesale & retail | 2010 |
| Janline Ky | Transport & logistics | 2019 |
| JarMore Oy | Professional & scientific | 2021 |
| Jarmat Oy | Manufacturing | 2000 |
| Jarme Oy | Professional & scientific | 2012 |
| Jauhiaisen Puutarha Oy | Agriculture & fishing | 1987 |
| JeRiBox Oy | Information & communication | 2025 |
| Jeloresta Oy | Real estate | 1998 |
| Jeolapp Oy | Other services | 2021 |
| Jofogo Oy | Real estate | 1997 |
| Jokiharjun hevospalvelut Oy | Education | 2023 |
| Jukara Oy | Construction | 2018 |
| Juki Remontit Oy | Construction | 2010 |
| Jukka Saastamoinen Oy | Real estate | 1988 |
| Juovva Oy | Hospitality | 1985 |
| Jussi LJK Oy | Manufacturing | 1993 |
| Jylhä Outdoors Oy | Arts & recreation | 2020 |
| K & K Mattinen Ky | Education | 2014 |
| K&R Riihola Oy | Hospitality | 2002 |
| KARO-Tuote Oy | Manufacturing | 2020 |
| KE-LE Design Oy | Professional & scientific | 2009 |
| KH-Tarkastus Oy | Administrative & support | 2009 |
| Kimerak OY | Construction | 2009 |
| KING R Oy | Professional & scientific | 2026 |
| KK-Koti Oy | Wholesale & retail | 2013 |
| KL JiiPee Oy | Transport & logistics | 2011 |
| KaSilla Kuntoon Ky | Education | 1994 |
| Kahdeksan Veljestä Oy | Hospitality | 2016 |
| Kahvila Hilla Oy | Hospitality | 2014 |
| Kaivu-Pojat Makkonen Oy | Real estate | 1979 |
| Kaivutyö Hynynen Oy | Construction | 2009 |
| Kamenka Oy | Administrative & support | 1996 |
| Kari Leinonen Ky | Agriculture & fishing | 1972 |
| Karu Store & Studio Oy | Wholesale & retail | 2010 |
| Karvion Portti Oy | Wholesale & retail | 2001 |