| Janne ja Tiina Toikka | Wholesale & retail | 2011 |
| Jepajemmaa Holding Oy | Financial services | 2025 |
| Johanna Kalliola Ky | Wholesale & retail | 2022 |
| Jorma Seppänen Kommandiittiyhtiö | Manufacturing | 1982 |
| Jovete Oy | Administrative & support | 2013 |
| Jtec Assembly Ky | Manufacturing | 2018 |
| JuMi Autotalo Oy | Wholesale & retail | 2023 |
| Jukka S. Lahtinen Ky | Real estate | 2012 |
| Jussi Salo Oy | Transport & logistics | 1994 |
| Juusii Ky | Manufacturing | 1986 |
| K&P Win Oy | Financial services | 2018 |
| K.Kosolan Huolto Oy | Other services | 2021 |
| Karipe OY | Construction | 2016 |
| KP Spedition Ab Oy | Transport & logistics | 2023 |
| Kuljetus T. Suominen Ky | Transport & logistics | 2011 |
| Kahvila Heinolan Palmu Oy | Hospitality | 1975 |
| Kahvila-Ravintola Kaprokki Ky | Hospitality | 1985 |
| Kallio Rent Sähköpyörät Oy | Arts & recreation | 2021 |
| Kastli Oy | Real estate | 1995 |
| Kauppahuone Vanha Mikko Oy | Wholesale & retail | 2025 |
| Kemplink Oy | Manufacturing | 2025 |
| Kiinteistö Oy Harkkotie 3 | Real estate | 2019 |
| Kiinteistö Oy Kalliopaju | Hospitality | 2014 |
| Kiinteistö Oy Koskisen pienteollisuustalo | Real estate | 1980 |
| Kiinteistö Oy Myllykangas | Real estate | 2012 |
| Kiinteistö Oy Nastolan Jousitie 7 | Real estate | 2024 |
| Kiinteistö Oy Nastolan Varikko | Real estate | 2005 |
| Kiinteistöhuolto Rantanen Oy | Administrative & support | 2014 |
| Kiinteistönuutti Oy | Real estate | 1995 |
| Kiinteistöyhtiö Tehdassora Oy | Real estate | 2004 |
| Kiviniemen Yläkartano Oy | Hospitality | 2015 |
| Kivisampo Oy | Manufacturing | 1961 |
| Kolmen kampuksen urheiluopisto oy | Education | 2022 |
| Koneurakointi Nurmela Oy | Construction | 2015 |
| Kontturi Consulting Oy | Professional & scientific | 2011 |
| Kotihoiva Niittytuuli Oy | Health & social care | 2020 |
| KuCa Group Oy | Manufacturing | 2024 |
| KuCa Module Oy | Manufacturing | 2024 |
| Kuivannon Kirjapaino Ky | Wholesale & retail | 1985 |
| Kuivannon Vesikunta | Water & waste | 1959 |
| Kukkasrinne Oy | Hospitality | 2021 |
| Kuljetus Timo Salo Oy | Transport & logistics | 1980 |
| Kuljetusliike Hermunen Oy | Transport & logistics | 2025 |
| Kuljetusliike M. Wallenius Oy | Transport & logistics | 2013 |
| Kumart Oy | Manufacturing | 1986 |
| Kurottajapalvelu Toivari Oy | Administrative & support | 1993 |
| König Nordic Oy | Wholesale & retail | 2025 |
| LT Consulting Oy | Professional & scientific | 2019 |
| LVI-Forsström Oy | Construction | 2021 |
| LaakkoSET Software Oy | Information & communication | 2026 |
| Lahden Kiinteistöpalvelu Oy | Real estate | 1999 |
| Lahden Kiinteistövaltti Oy | Administrative & support | 2022 |
| Lahden Lvi-Fix Oy | Construction | 2025 |
| Lahden PT Rakennus Oy | Construction | 2011 |
| Lahden Pystysaumaus Oy | Construction | 2001 |
| Lahden Sähkö ja Suunnittelu Oy | Construction | 2025 |
| Lankatien tallit Oy | Real estate | 2014 |
| Larus Finland Oy | Real estate | 1989 |
| Lempin Koti Oy | Health & social care | 2020 |
| Levypyörä Oy | Manufacturing | 1955 |
| Loistoremontit Oy | Construction | 2007 |
| Louhos Investments Oy Ab | Financial services | 2022 |
| Low Key Machine Oy | Professional & scientific | 2000 |
| LämpöSäästö Oy | Construction | 2025 |
| Länsikarhu Oy | Wholesale & retail | 2004 |
| MJW-Yhtiö Oy | Real estate | 2006 |
| ML-Rakennus Oy | Construction | 2022 |
| MLO Equine Trade & Consulting Oy | Wholesale & retail | 2026 |
| MPK-Koneistus Oy | Manufacturing | 2008 |
| MR-Auto Oy | Other services | 2004 |
| MR-Nosto Oy | Construction | 2006 |
| MT Betoniteräs Oy | Construction | 2009 |
| MakeTrans Holding Oy | Financial services | 2022 |
| Mapa-inssit Oy | Professional & scientific | 2004 |
| Maps FN Oy | Information & communication | 2025 |
| Martti Piironen Ky | Manufacturing | 1986 |
| Matt-Metal Oy | Manufacturing | 2006 |
| Maylle Oy | Construction | 2026 |
| Mediseam Oy | Manufacturing | 1987 |
| Megabitti Oy | Information & communication | 2022 |
| Metallisorvaamo A. Pakarinen Oy | Manufacturing | 1995 |
| MieBet Oy | Manufacturing | 2019 |
| Mitosis Oy | Construction | 2004 |
| Mittapaikoitus Oy | Manufacturing | 1994 |
| Mopasol Oy | Information & communication | 2001 |
| Morobel Oy | Real estate | 2022 |
| N&H Finntrans Oy | Transport & logistics | 2011 |
| Nastainvest OY | Financial services | 2023 |
| Nasto-Rengas OY | Wholesale & retail | 2002 |
| NT Urheilu Oy | Arts & recreation | 2013 |
| Naskone ky | Wholesale & retail | 1985 |
| Nasto Siivous Ky | Administrative & support | 1985 |
| Nastolan AJ-Remontit Oy | Construction | 2013 |
| Nastolan Autopalvelu Tapsa Oy | Other services | 1981 |
| Nastolan Forest Huolto Oy | Manufacturing | 1990 |
| Nastolan Fysikaalinen Hoitolaitos Oy | Health & social care | 1984 |
| Nastolan Hautaustoimisto Oy | Other services | 2020 |
| Nastolan Isännöintipalvelu Oy | Professional & scientific | 1994 |
| Nastolan Kellohuolto Oy | Other services | 2022 |
| Nastolan Kiinteistönotariaatti Oy | Real estate | 1991 |