| Connect Electro AS | Oslo | 2012 |
| Connect Es Nuf | Chichester, West Sussex Po18 0Tu | 2014 |
| Connect Hub AS | Oslo | 2020 |
| Conrad Bygg AS | Svolvær | 2013 |
| Conseal AS | Oslo | 1975 |
| Consem Entreprenør AS | Råde | 2004 |
| Consepto Elektro AS | Trondheim | 2018 |
| Consist AS | Ridabu | 2017 |
| Consolvo AS | Tranby | 1987 |
| Consta AS | Oslo | 2023 |
| Constant Bygg AS | Kongsberg | 2018 |
| Consto Anlegg AS | Skedsmokorset | 1986 |
| Consto Anlegg Midt AS | Trondheim | 2018 |
| Consto Anlegg Nord AS | Bodø | 2016 |
| Consto Anlegg Sør AS | Arendal | 2019 |
| Consto Anlegg Vest AS | Bergen | 2020 |
| Consto Anlegg Øst AS | Skedsmokorset | 2015 |
| Consto AS | Tromsø | 2010 |
| Consto Bergen AS | Bergen | 2005 |
| Consto Dambygg AS | Sunde I Sunnhordland | 2017 |
| Construcciones Metalicas Biok S.L. | Es-20014 Donostia, Gipuzkoa | 2019 |
| Construcciones Metálicas Comansa | Es-31620 Huarte | 2023 |
| Construct Vision AS | Laksevåg | 2024 |
| Constructe AS | Oslo | 2023 |
| Construction City Bygg AS | Oslo | 2021 |
| Construction Concepts AS | Oslo | 2026 |
| Construction Solution Service Nuf | Oslo | 2015 |
| Construction Team Norway AS | Gressvik | 2015 |
| Construction-Uslugi Budowlane | 83-200 Starogard Gdansk | 2009 |
| Constructum AS | Gressvik | 2015 |
| Constructum Core AS | Gressvik | 2026 |
| Consulting-Ua Ltd | Ua 02002 Kiev | 2022 |
| Conta Bygg AS | Bergen | 2018 |
| Container Og Kuldeservice AS | Ålesund | 2000 |
| Contanest AS | Søreidgrend | 2025 |
| Contea Group AS | Oslo | 2019 |
| Contenti AS | Oslo | 2022 |
| Continent Montage Aktiebolag | Mysen | 1998 |
| Contour Advanced Systems B.V | 7051Cm Varsseveld | 2022 |
| Contrack AB | Se-781 92 Borlänge | 2023 |
| Contracting Rafal Gubala | Pl-74300 Mysliborz | 2007 |
| Contractor AS | Gressvik | 2025 |
| Contractor Bygg AS | Sandnessjøen | 2013 |
| Contrast Malerfirma AS | Sæbøvågen | 2023 |
| Contre AS | Østre Gausdal | 2022 |
| Contreat AS | Mjøndalen | 2019 |
| Contur AS | Kristiansand S | 2021 |
| Convergint Norway AS | Oslo | 2022 |
| Conx Svenska | Fetsund | 2023 |
| Coolteam AS | Oslo | 2005 |
| Coolteam Bergen AS | Arnatveit | 2015 |
| Coolteam Midt-Norge AS | Trondheim | 2017 |
| Cooltech AS | Melhus | 2026 |
| Cooltech Industriservice AS | Kvelde | 2021 |
| Copuno Norway | Es-25125 Alguaire | 2016 |
| Copuno Sweden AB Nuf | Oslo | 2015 |
| Corda AS | Oslo | 2016 |
| Corda Group AS | Oslo | 2022 |
| Coreborn Plus Procesos Productivos SL | Es-28013 Madrid | 2025 |
| Coreoptics AS | Auli | 2025 |
| Coretto AS | Sandnes | 2018 |
| Corianita AS | Torød | 2016 |
| Corigo AS | Oslo | 2021 |
| Cornelius Byggetjenester AS | Grimstad | 2016 |
| Cornelius De Graaff Holding AS | Breim | 2021 |
| Corneliussen AS | Sandnes | 2014 |
| Coromatic AB | Se-168 67 Bromma | 2018 |
| Corotek Nordic AS | Hamar | 2015 |
| Corpro Systems Limited Nuf | Stavanger | 2002 |
| Correct Bygg AS | Østerås | 2014 |
| Correct Invest AS | Lillestrøm | 1986 |
| Corrotech OY | Fi-95440 Torneå | 2015 |
| Cosermo Espanola Construcciones Servicios Y Montajes SL | Es-33211 Gijon (Asturias) | 2023 |
| Cosmic Bygg AS | Sandefjord | 1985 |
| Cosmin Bygg AS | Vrådal | 2022 |
| Costa PT AS | Trondheim | 2012 |
| Cosumelt Oü Nuf | 13515 Tallin | 2011 |
| Countach Montasje AS | Haugesund | 2026 |
| Countryhouse Building Oü | Ee-65201 Vastseliina | 2022 |
| Coupe Holding AS | Førde | 2015 |
| Couto Gård AS | Averøy | 2021 |
| Covei AS | Kokstad | 2021 |
| Cover Group AS | Hokksund | 2024 |
| CR Bygg AS | Revetal | 2021 |
| CR Bygg Holding AS | Revetal | 2021 |
| CR Maskin Og Utemiljø AS | Notodden | 2024 |
| CR Tech AS | Gardermoen | 2018 |
| Craft Bygg AS | Oppegård | 2021 |
| Craft Eiendom AS | Steinsland | 2010 |
| Craft Entreprenør AS | Steinsland | 2017 |
| Craft Holding AS | Steinsland | 2012 |
| Craft Service AS | Stavanger | 2024 |
| Craftel AS | Narvik | 2025 |
| Craftify AS | Oslo | 2012 |
| Craftman AS | Dilling | 2024 |
| Craftsmen AS | Nesoddtangen | 2019 |
| Craftwear AS | Søgne | 2021 |
| Crane Norway Group AS | Sandnes | 2016 |
| Crane Norway Midt-Norge AS | Melhus | 1989 |
| Crane Norway Vest AS | Sandnes | 1979 |