Women who carry a germline mutation in either the BRCA1 or BRCA2 gene face a lifetime risk of breast cancer of up to 70%, and once they receive a diagnosis of breast cancer, they face high risks of both second primary breast and ovarian cancers. Preventive bilateral salpingo-oophorectomy is recommended to women with a BRCA mutation at age 35 years or thereafter to prevent breast and ovarian cancer, but it is unclear whether oophorectomy has an impact on survival in women with BRCA-associated breast cancer.To estimate the impact of oophorectomy on survival in women with breast cancer with a BRCA1 or BRCA2 mutation.Retrospective analysis of patients selected by pedigree review of families who received counseling at 1 of 12 participating clinical genetics centers. Patients were 676 women with stage I or II breast cancer and a BRCA1 or BRCA2 mutation who were observed for up to 20 years after receiving a diagnosis between 1975 and 2008. Survival experience was compared for women who did and who did not undergo oophorectomy.In all analyses, the primary end point was death due to breast cancer.Of the 676 women, 345 underwent oophorectomy after the diagnosis of breast cancer and 331 retained both ovaries. The 20-year survival for the entire patient cohort was 77.4%. The adjusted hazard ratio for death attributed to breast cancer in women who underwent oophorectomy was 0.38 (95% CI, 0.19-0.77; P = .007) for BRCA1 carriers and 0.57 (95% CI, 0.23-1.43; P = .23) for BRCA2 carriers. The hazard ratio for breast cancer-specific mortality was 0.76 (95% CI, 0.32-1.78; P = .53) for women with estrogen receptor-positive breast cancer and 0.07 (95% CI, 0.01-0.51; P = .009) for women with estrogen receptor-negative breast cancer.Oophorectomy is associated with a decrease in mortality in women with breast cancer and a BRCA1 mutation. Women with estrogen receptor-negative breast cancer and a BRCA1 mutation should undergo oophorectomy shortly after diagnosis.