| Mårfellen Holding AS | Professional & scientific | 2023 |
| Mørkholt Invest AS | Real estate | 2006 |
| Møtestad Seljord AS | Administrative & support | 2000 |
| Nenseter Holding AS | Professional & scientific | 2016 |
| Nordbygdi Eiendom AS | Real estate | 2021 |
| Nordbygdi Eigedom AS | Real estate | 2005 |
| Nordbygdi Eigedomselskap AS | Real estate | 2021 |
| Nordbygdi Handel AS | Wholesale & retail | 2021 |
| Nordbygdi Holding AS | Wholesale & retail | 2021 |
| Nordbygdi Invest AS | Real estate | 2012 |
| Nordbygdi Næringseiendom AS | Real estate | 2023 |
| Nordbygdivegen 200 Seljord AS | Real estate | 2019 |
| Nordstoga AS | Real estate | 2021 |
| Norsk Linjeboring AS | Manufacturing | 2024 |
| Nyveg 3 Eigedom AS | Real estate | 2016 |
| Ofte AS | | 2017 |
| Omtveit Holding AS | Financial services | 2013 |
| Radiolink Telemark AS | Information & communication | 2007 |
| Randheim Holding AS | | 2022 |
| Reinstaul Kraft AS | Energy | 2012 |
| Rett AS | Transport & logistics | 2011 |
| Ringmyri AS | | 2022 |
| RS Rådgivning AS | Professional & scientific | 2026 |
| Sande Rue Skogsdrift Ans | Agriculture & fishing | 1994 |
| Selaker Holding AS | Real estate | 2005 |
| Seljord Auto-Senter AS | Wholesale & retail | 1982 |
| Seljord Bil AS | Wholesale & retail | 1992 |
| Seljord Bilopphuggeri AS | Wholesale & retail | 2016 |
| Seljord Blomster Og Hagesenter AS | Agriculture & fishing | 2013 |
| Seljord Bygg & Maskinutleige AS | Administrative & support | 2025 |
| Seljord Elektriske Eigedom AS | Real estate | 2005 |
| Seljord Elektriske Eigedomsutvikling AS | Real estate | 2019 |
| Seljord Ferieland AS | Hospitality | 2002 |
| Seljord Festivaldrift AS | Real estate | 1993 |
| Seljord Fjelltjeneste AS | Education | 2001 |
| Seljord Hestesenter AS | Education | 2011 |
| Seljord Hotell AS | Hospitality | 2013 |
| Seljord Hotell Eiendom AS | Real estate | 2010 |
| Seljord Invest AS | Real estate | 2001 |
| Seljord Landbruk Og Maskin AS | Wholesale & retail | 2008 |
| Seljord Maskinutleige AS | Administrative & support | 2022 |
| Seljord Motell AS | Hospitality | 2000 |
| Seljord Næringsbygg AS | Real estate | 2008 |
| Seljord Næringseiendom AS | Real estate | 2023 |
| Seljord Næringseiendom Holding AS | Real estate | 2023 |
| Seljord Radio Og TV AS | Other services | 1987 |
| Seljord Rekneskaps-Service AS | Professional & scientific | 1974 |
| Seljord Sport Og Fritid AS | Transport & logistics | 2007 |
| Seljord Taxi Da | Transport & logistics | 2019 |
| Seljord Varmepumpe AS | Construction | 2018 |
| Seljord Vedfabrikk Ans | Manufacturing | 1990 |
| Seljord Veterinærkontor AS | Professional & scientific | 2010 |
| Seljordsvatnet Grunneigarlag SA | Real estate | 1994 |
| Sigstad Eigedom AS | Real estate | 1996 |
| Siloen Gardsbutikk AS | Wholesale & retail | 2018 |
| SJ Maskin & Service AS | Wholesale & retail | 2014 |
| Sjøormen Produksjon AS | Arts & recreation | 2012 |
| Skorve Entreprenør AS | Construction | 2010 |
| Slaatto Rør AS | Construction | 2016 |
| SN Eigedom AS | Real estate | 2016 |
| Sollid AS | Construction | 2020 |
| Sollid Consult AS | Professional & scientific | 2013 |
| Star Bilskade Seljord AS | Other services | 2023 |
| Steinsrudvegen Næringseiendom AS | Real estate | 2023 |
| Storøy Skogsbilveglag SA | Real estate | 1989 |
| Sunhill Invest AS | Professional & scientific | 2005 |
| Svenseid Tunet SA | Real estate | 2001 |
| Sør-Norsk Entreprenør AS | Education | 2019 |
| T. Tveitan AS | Wholesale & retail | 1987 |
| Tarjei Skræi Handel AS | Wholesale & retail | 2013 |
| TB Holding Seljord AS | | 2026 |
| Telemark Bilruter AS | Transport & logistics | 1972 |
| Telemark Bilruter Buss AS | Transport & logistics | 1998 |
| Telemark Bilruter Eigedom AS | Transport & logistics | 2017 |
| Telemark Gods AS | Transport & logistics | 2026 |
| Telemark Gods Og Miljø AS | Transport & logistics | 2026 |
| Telemark Miljøservice AS | Transport & logistics | 2026 |
| Telemark Resirk AS | Transport & logistics | 2026 |
| Telemark Transportservice AS | Transport & logistics | 2008 |
| Telerevisjon AS | Professional & scientific | 2006 |
| Telesenteret Seljord AS | Wholesale & retail | 1999 |
| Telesport AS | Wholesale & retail | 1990 |
| The Literary Oak AS | Arts & recreation | 2024 |
| Torsdalen Holding AS | | 2025 |
| Truckpartner Telemark AS | Other services | 2022 |
| Tuften Holding AS | | 2005 |
| Tussefløti Invest AS | | 2026 |
| Tveiten Kraft AS | Energy | 2004 |
| Utleieboliger Seljord Da | Real estate | 2009 |
| V.S. Holding AS | Real estate | 2023 |
| Valhovd AS | Manufacturing | 2024 |
| Valhovd Invest AS | Manufacturing | 2024 |
| Varmehandel AS | Wholesale & retail | 2007 |
| Veglaget Millionvegen SA | Real estate | 1975 |
| Vest Telemark Bok Og Papir AS | Wholesale & retail | 2000 |
| Vest Telemark Kiropraktorklinikk AS | Health & social care | 2022 |
| Vest Telemark Varmepumpe AS | Construction | 2025 |
| Vest-Telemark Synssenter AS | Wholesale & retail | 1997 |
| Vestfold Og Telemark Prosjektutvikling AS | Professional & scientific | 1986 |
| Vidar Tveiten AS | Real estate | 2023 |