Purpose: To evaluate whether previous ovarian removal concomitant with benign hysterectomy improves prognosis in a cohort of women with breast cancer. Methods: In this nationwide register-based cohort study, risk of recurrence and mortality were examined in 4563 women with invasive breast cancer and previous bilateral salpingo-oophorectomy (BSO) concomitant with benign hysterectomy, during 1977–2018. Comparing with benign hysterectomy alone, hazard ratios (HRs) and 95% confidence intervals (CIs) were evaluated by Cox-proportional hazards regression models. Analyses were stratified on age at hysterectomy as a proxy for menopausal status (< 45, 45–54 and ≥ 55 years); tumor characteristics, estrogen receptor (ER)-status, and use of hormone therapy (HT) were included in multivariable models. Results: Compared with hysterectomy alone, premenopausal (< 45 years) BSO at benign hysterectomy was associated with an age and calendar period adjusted HR of 1.48 (95% CI 0.83–2.65) for breast cancer recurrence within 10 years of follow-up, a HR of 1.07 (95% CI 0.66–1.72) for overall mortality after breast cancer, and a HR of 0.59 (95% CI 0.26–1.32) for breast cancer-specific mortality. The corresponding HRs for postmenopausal (≥ 55 years) BSO at benign hysterectomy were 1.51 (95% CI 0.73–3.12) for recurrences, 1.34 (95% CI 0.74–2.44) for overall mortality, and 1.78 (95% CI 0.74–4.30) for breast cancer mortality. Adjusting for tumor characteristics, ER-status and HT did not alter the results. Conclusion: Results from this cohort study did not indicate an improvement in breast cancer prognosis when removing the ovaries at benign hysterectomy prior to the cancer diagnosis.