| Klarvinduer AS | Oslo | 2021 |
| Klas AS | Levanger | 1985 |
| Klashaugen Eiendom AS | Lillehammer | 2002 |
| Klashaugen Entreprenør AS | Lillehammer | 2017 |
| Klashaugen Holding AS | Lillehammer | 2005 |
| Klassisk Skigard Nuf | 33334 Suginciu Km., Moletu Raj. | 2020 |
| Klassix Eesti Nuf | Ee-13516 Harjumaa | 2019 |
| Klasvoll Eiendom AS | Sørkjosen | 1992 |
| Klatt Ans | Oslo | 2013 |
| Klaudesta Uab Nuf | Lt-05217 Vilnius | 2024 |
| Klaus Karlsen Maskinentreprenør AS | Bleik | 1997 |
| Klausen Elektro AS | Rossfjordstraumen | 2010 |
| Klausen Multiservice AS | Risør | 2024 |
| Klaveness Maler- Og Byggmester- Forretning AS | Oslo | 2004 |
| Klavestad-Entreprenør AS | Sarpsborg | 2012 |
| KLB Montering AS | Kjeller | 2025 |
| Kleab Klaveness Alarm & Elteknikk AS Norsk Avdeling Av Utenlandsk Foretak Nuf | Se-681 43 Kristinehamn | 2002 |
| Klebra AS | Ankenes | 2026 |
| Kleemann Services Ltd, Cyprus | Cy-1086 Nicosia | 2021 |
| Kleffmann-Einrichtungen Limited Zweigniederlassung Deutscland | Drammen | 2009 |
| Kleivan Bygg & Maskin AS | Tinn Austbygd | 2016 |
| Kleivanveien 15 AS | Oslo | 2012 |
| Kleiven Drift AS | Melhus | 2026 |
| Kleiven Sogn AS | Årdalstangen | 1987 |
| Kleiven Sogn Eigedom AS | Årdalstangen | 1989 |
| Klemetsrud Grave Og Sprengeservice AS | Oslo | 2015 |
| Klemma Bygg Og Service AS | Noresund | 2024 |
| Klemma Invest AS | Hønefoss | 2005 |
| Klemmetsmo AS | Sandefjord | 2010 |
| Klempe Maskin Og Transport AS | Norddal | 2022 |
| Klenevåg Maskin Da | Dale I Sunnfjord | 2016 |
| Klepp Maskin Og Transport AS | Steinkjer | 2024 |
| Klepp Service Drift AS | Klepp Stasjon | 2015 |
| Kleppe Byggservice AS | Klokkarvik | 2017 |
| Kleppe Multiservice AS | Byrkjelo | 2022 |
| Kleppe Q & Maskin AS | Fotlandsvåg | 2011 |
| Kleppseter Anlegg AS | Stathelle | 2018 |
| Klette Bygg Og Montasje AS | Bodø | 2025 |
| Klette Elektro AS | Voss | 2018 |
| Kleveland AS | Kristiansand S | 1996 |
| Kleveland Holding AS | Kristiansand S | 2005 |
| Kleven AS | Alta | 2022 |
| Kleven Bygg & Anlegg AS | Gol | 2021 |
| Kleven Bygg Eiendom AS | Oppdal | 2015 |
| Kleven Bygg Holding AS | Oppdal | 2015 |
| Kleven Bygg Invest AS | Oppdal | 2015 |
| Kleven Bygg Oppdal AS | Oppdal | 2015 |
| Kleven Maskin AS | Skui | 2023 |
| Klever Bygg AS | Nesttun | 2025 |
| Klever Bygg Og Utemiljø AS | Isfjorden | 2014 |
| Klevstad Rørservice AS | Nyborg | 2018 |
| KLF Holding AS | Skien | 2014 |
| Klim-Jas Ventilasjon AS | Nesøya | 2026 |
| Klima & Automatikk AS | Malm | 2001 |
| Klima & Montasje AS | Ringebu | 2018 |
| Klima AS | Vanse | 2026 |
| Klima Boligventilasjon AS | Askim | 2022 |
| Klima Experten AS | Florø | 2008 |
| Klima Facility AS | Nesttun | 2009 |
| Klima Konstrukt AS | Sander | 2019 |
| Klima Og Bygg AS | Oslo | 2005 |
| Klima Og Bygg Holding AS | Oslo | 2020 |
| Klima Og Energiteknikk AS | Sauda | 1988 |
| Klima Og Kuldeteknikk A/S | Trondheim | 1988 |
| Klima Og Ventilasjon AS | Moss | 2022 |
| Klima Øst AS | Grålum | 2007 |
| Klima-Energi AS | Løten | 2023 |
| Klima-Sør AS | Risør | 1990 |
| Klima-Trond AS | Tyristrand | 2018 |
| Klimaanlegg AS | Vanse | 2021 |
| Klimabefuktning AS | Drøbak | 2025 |
| Klimabygg AS | Straumsgrend | 2019 |
| Klimacomfort AS | Stavanger | 2017 |
| Klimacomfort Service AS | Stavanger | 2023 |
| Klimaconsult AS | Sande I Vestfold | 2004 |
| Klimaexpressen AS | Strandebarm | 2023 |
| Klimafag AS | Rjukan | 2013 |
| Klimafix AS | Laksevåg | 2013 |
| Klimakoden AS | Kleppestø | 2024 |
| Klimakompetanse AS | Oslo | 2012 |
| Klimakontakten AS | Bødalen | 2015 |
| Klimaoprema D.D. Nuf | Hr-10430 Samobor | 2021 |
| Klimapartner AS | Langhus | 2025 |
| Klimapro AS | Tiller | 1993 |
| Klimarens AS | Vormedal | 2025 |
| Klimaservice AS | Sandnes | 1983 |
| Klimaservice AS | Bardu | 1986 |
| Klimaservice Modum AS | Åmot | 2012 |
| Klimaservice Og Transport AS | Oslo | 2012 |
| Klimaservice Oslo AS | Oslo | 2015 |
| Klimaspesialisten AS | Krokelvdalen | 2021 |
| Klimateam AS | Charlottenlund | 2004 |
| Klimatech AS | Larvik | 2025 |
| Klimatekk AS | Florø | 2014 |
| Klimateknikk AS | Sandnessjøen | 1996 |
| Klimateknikk Oslo AS | Oslo | 2004 |
| Klimateknikk.As AS | Røyken | 2015 |
| Klimatjenester AS | Furnes | 2003 |
| Klimex Piotr Klincewicz | Pl-66-400 Gorzow Wielkopolski | 2014 |
| Klinge Bygg AS | Rasta | 2018 |