| Brendebakken Verk AS | Administrative & support | 2004 |
| Brenden Allservice Nuf | Construction | 2019 |
| Breunig Holding AS | | 2024 |
| Brevetti Nordic AS | Wholesale & retail | 2018 |
| Briani Cafe Og Selskapsmat AS | Hospitality | 1992 |
| Briani Catering Og Selskapsmat AS | Hospitality | 2010 |
| Bright Future AS | Financial services | 2006 |
| Bright People Eiendom AS | Real estate | 2024 |
| Bright Rådgivende Ingeniører VVS AS | Professional & scientific | 2004 |
| Brigt Olav Vik AS | Information & communication | 2012 |
| Brillbird, Drammen Negledesign AS | Other services | 2015 |
| Briole Holding AS | Professional & scientific | 2003 |
| Bris Regnskap AS | Professional & scientific | 2025 |
| Briskeby Forvaltning AS | Hospitality | 2003 |
| Brocap AS | | 2026 |
| Broka Invest AS | Professional & scientific | 2014 |
| Broken Pineapple AS | | 2023 |
| Bromunch AS | Hospitality | 2022 |
| Bronchus AS | Health & social care | 2018 |
| Bronstad Holding AS | | 2025 |
| Bror Meyer Holding AS | | 2005 |
| Browcity AS | Other services | 2022 |
| BRT Services AS | Transport & logistics | 2016 |
| Brude Kolstad AS | Construction | 2005 |
| Brudepikene AS | Other services | 2007 |
| Brudesenteret AS | Wholesale & retail | 1993 |
| Brumbas AS | Professional & scientific | 2005 |
| Brusetveien 60 AS | Real estate | 2012 |
| Bruun Eiendomsselskap AS | Real estate | 2021 |
| Bruun Invest AS | Real estate | 2005 |
| Bruun Johansen Eiendom Da | Real estate | 2002 |
| Bruusgaard K15 AS | Financial services | 2005 |
| Bruusgaard Vika AS | Real estate | 2004 |
| Brynjar Geir Innovation AS | Professional & scientific | 1998 |
| Brånåsen Eiendom AS | | 2022 |
| Brække Boligutvikling AS | Real estate | 2025 |
| Brække Da | | 1989 |
| Brække Eiendom AS | Real estate | 2010 |
| Brække Holding AS | Construction | 2018 |
| Brække Melbye Holding AS | Real estate | 2006 |
| Brødrene D&K Blikk Og Tak AS | Construction | 2022 |
| Brøk Byggeteknikk AS | Professional & scientific | 2020 |
| Brøttet Barnehage SA | Education | 2005 |
| BT Berg Holding AS | Professional & scientific | 2017 |
| BT Ortopedi AS | Manufacturing | 1990 |
| Bt-Invest AS | | 2019 |
| BTC Ans | Construction | 2006 |
| Btcaj AS | Health & social care | 2019 |
| Btni Holding AS | Wholesale & retail | 2021 |
| Bto Holding AS | Real estate | 2010 |
| Bu 3S AS | | 2014 |
| Bugbear Holding AS | | 2025 |
| Buktaveien AS | Real estate | 2018 |
| Bul Bygg AS | Construction | 2017 |
| Bulk Product Carrier SA | | 2001 |
| Bulkfix.No AS | Other services | 2016 |
| Bull Invest Drammen AS | Real estate | 2000 |
| Bulle Invest AS | Professional & scientific | 2007 |
| Bullish AS | | 2025 |
| Burgerland AS | Hospitality | 2016 |
| Business and Pleasure AS | Wholesale & retail | 2021 |
| Business Is Sport AS | Professional & scientific | 1982 |
| Business Management AS | Professional & scientific | 2004 |
| Busken Bygg AS | Real estate | 2008 |
| Busken Eiendom AS | Real estate | 2020 |
| Buskerud Antirust AS | Other services | 2016 |
| Buskerud Auto Nuf | Wholesale & retail | 2005 |
| Buskerud Begravelsesbyrå AS | Other services | 2005 |
| Buskerud Bilutleie AS | Administrative & support | 2018 |
| Buskerud Bilvask & Bilpleie AS | Other services | 2014 |
| Buskerud Blikk & Montasje AS | Construction | 2002 |
| Buskerud Blikk & Sveis AS | Construction | 1993 |
| Buskerud Blikk Holding AS | Construction | 2005 |
| Buskerud Brannservice AS | Wholesale & retail | 2010 |
| Buskerud Brød AS | Wholesale & retail | 2013 |
| Buskerud Byggrådgivning AS | Professional & scientific | 2017 |
| Buskerud Ferdigplen AS | Agriculture & fishing | 2025 |
| Buskerud Monument Arthur Berntzen AS | Manufacturing | 1981 |
| Buskerud Mynt, Gull Og Sølv Avd. Drammen AS | Wholesale & retail | 2020 |
| Buskerud Næringsmegling AS | Real estate | 1999 |
| Buskerud Og Vestfold Trav Holding AS | Arts & recreation | 2014 |
| Buskerud P.G. Invest AS | Manufacturing | 2005 |
| Buskerud Skadedyrkontroll AS | Administrative & support | 2019 |
| Buskerud Snekker AS | Construction | 2024 |
| Buskerud Tungbilservice AS | Other services | 2026 |
| Buskerud Utemiljø AS | Construction | 2025 |
| Buskerud Varmepumpeservice AS | Construction | 2008 |
| Buskerudveien 117 AS | Real estate | 2005 |
| Buskerudveien Invest AS | Professional & scientific | 2019 |
| Busy AS | Construction | 2013 |
| Busy Eiendom AS | Real estate | 2024 |
| Bvi 72 AS | Real estate | 2013 |
| BVR Worldtrade Da | Wholesale & retail | 2010 |
| Bwrr AS | Professional & scientific | 2013 |
| By Lokal AS | Information & communication | 2022 |
| By T&B Da | Wholesale & retail | 2010 |
| Byarkitekten AS | Professional & scientific | 2003 |
| Byen Vår Drammen AS | Other services | 1992 |
| Bygg & Eiendoms Service AS | Administrative & support | 1987 |
| Bygg Norge AS | Construction | 2024 |