Abstract Background There are very few long-term Canadian data on breast cancer outcomes by stage. We described the stage, treatment and outcomes of breast cancer at a population level for patients in British Columbia. Methods This population-based cohort study included almost all patients with incident breast cancer registered in 2002 (about 97.6% registry case completeness). For these patients, information on stage, primary local surgery, radiotherapy, chemotherapy, hormone therapy and survival outcome (based on registry date and cause-of-death data) were available. We calculated Kaplan–Meier curves for breast cancer–specific survival and overall survival by stage and analyzed prognostic and treatment factors with a multivariable Cox model. Results The 2927 incident cases of breast cancer identified in 2002 had the following distribution by stage: stage 0 (in situ), 424 (14%); stage I, 1118 (38%); stage II, 938 (32%); stage III, 233 (8%); stage IV, 123 (4%); unknown, 91 (3%). The distribution of patients’ ages was < 40 years, 127 (4%); 40–49, 538 (18%); 50–59, 719 (25%); 60–69, 660 (23%); 70–79, 583 (20%); ≥ 80, 300 (10%). Within the first year after diagnosis, radiotherapy was provided to 1649 patients (56%), chemotherapy to 928 (32%) and hormone therapy to 1664 (57%). Ten-year breast cancer–specific survival rates by stage were > 99% for stage 0, 95% for stage I, 81% for stage II, 55% for stage III and 4% for stage IV. Ten-year overall survival rates were 89% for stage 0, 81% for stage I, 68% for stage II, 43% for stage III and 2% for stage IV. Interpretation This analysis provides a Canadian benchmark for treatment rates and 10-year outcomes by stage for all incident cases of breast cancer in a single province. Outcomes in British Columbia compared well with published rates for the United States and Europe.