Aim: Our previous population-based research found prophylactic surgery (hysterectomy and bilateral salpingo-oophorectomy [BSO]) halved the mortality risk for premenopausal breast cancer patients. Here we aim to replicate findings in a Western Australia dataset. Method: Data from the Western Australia Cancer Registry of 15 395 women 20–79 years diagnosed with primary breast cancer (1997–2011) was categorized into four groups: neither hysterectomy nor BSO, hysterectomy only, BSO only, or hysterectomy + BSO. We fitted flexible parametric breast cancer–specific and overall survival models with 95% confidence intervals (also known as Royston–Parmar models) to assess the impact of prophylactic surgery. Results: A total of 12 630 (82.0%) patients had no surgery, 1799 (11.7%) had a hysterectomy only, 337 (2.2%) had BSO only and 629 (4.1%) had both a hysterectomy and BSO. For all-causes mortality, unadjusted 10-year survival was highest for women who had either a hysterectomy + BSO (84.7%) or a hysterectomy only (84.2%). After adjusting for covariates, the survival advantage compared to women without any surgery remained significant for the hysterectomy only group (hazard ratio [HR] = 0.89; 95% confidence interval [CI], 0.81–0.98; P = 0.02). A similar pattern emerged in breast cancer–specific survival with significantly improved survival for women who had a hysterectomy only (HR = 0.83; 95% CI, 0.74–0.94; P = 0.003). However, for non-breast cancer-related survival, having a BSO alone increased risk of death (HR = 1.83; 95% CI, 1.14–2.93; P = 0.01). Conclusion: We observed significantly improved overall and breast cancer-specific survival among women who had a hysterectomy only, but increased non-breast cancer-related risk after BSO only. Breast cancer patients must weigh up pros and cons of prophylactic surgery.