Few studies have examined long-term suicide risk among breast cancer survivors, and there are no data for women in the United States. We quantified suicide risk through 2002 among 723,810 1-year breast cancer survivors diagnosed between January 1, 1953, and December 31, 2001, and reported to 16 population-based cancer registries in the United States and Scandinavia. Among breast cancer survivors, we calculated standardized mortality ratios (SMRs) and excess absolute risks (EARs) compared with the general population, and the probability of suicide. We used Poisson regression likelihood ratio tests to assess heterogeneity in SMRs; all statistical tests were two-sided, with a .05 cutoff for statistical significance. In total 836 breast cancer patients committed suicide (SMR = 1.37, 95% confidence interval [CI] = 1.28 to 1.47; EAR = 4.1 per 100,000 person-years). Although SMRs ranged from 1.25 to 1.53 among registries, with 245 deaths among the sample of US women (SMR = 1.49, 95% CI = 1.32 to 1.70), differences among registries were not statistically significant (P for heterogeneity = .19). Risk was elevated throughout follow-up, including for 25 or more years after diagnosis (SMR = 1.35, 95% CI = 0.82 to 2.12), and was highest among black women (SMR = 2.88, 95% CI = 1.44 to 5.17) (P for heterogeneity = .06). Risk increased with increasing stage of breast cancer (P for heterogeneity = .08) and remained elevated among women diagnosed between 1990 and 2001 (SMR = 1.36, 95% CI = 1.18 to 1.57). The cumulative probability of suicide was 0.20% 30 years after breast cancer diagnosis.