Women with germline BRCA1 mutation have a significant risk of breast and/or ovarian cancer. Prophylactic bilateral mastectomy (PBM) and prophylactic bilateral salpingo-oophorectomy (PBSO) prevent cancer in mutation carriers. The cost-effectiveness of PBSO (age of 35 years) with or without PBM five years earlier was compared to a no intervention setting employing a marginal cost analysis. National data on cancer incidence, mortality rates and costs were implemented together with observed Norwegian BRCA1 data in a Markov model and PBSO was assumed to reduce the risk of ovarian cancer by 90%. A 3% discount rate was used. The additional health care cost per mutation carrier undergoing PBSO and PBM was euro 15,784, and 6.4 discounted life years gained (LYG) was indicated (PBSO alone with 100% acceptance 3.1 LYG). The additional cost per LYG was euro 1973 (PBSO alone euro 1749/LYG). Including all resource use, the figure was a cost of euro 496 and euro 1284 per LYG, respectively. PBSO with or without PBM in BRCA1 mutation carriers is cost-effective. A testing of all incident breast cancers to identify mutation carrying families should be explored.