ABSTRACT Background Although small, node-negative breast cancer (i.e., T1abN0) constitutes 20% of all newly diagnosed breast cancers, data on prognosis and prognostic factors are limited. Methods We conducted a population-based cohort study including 20,114 Swedish women treated for T1abN0 breast cancer 1977 onwards. Patient and tumor data were collected from Swedish breast cancer registries. Cohort subjects were followed through linkage to the Cause of Death Register. We calculated the cumulative incidence of breast cancer specific and overall death, and used Cox regression to estimate hazard ratios (HRs) and 95% confidence intervals (CIs). Results During a median follow-up of 9.1 years (range 0-38), 915 women died of breast cancer and 5,416 of any cause. The 10-, 20- and 30-year cumulative incidence of breast cancer death was 3.4% (95% CI = 3.1 to 3.7%), 7.6% (95% CI = 7.1 to 8.2%) and 10.5% (95% CI = 9.6 to 11.4%), respectively. The multivariable HRs and 95% CIs of breast cancer death was 0.92 (0.88 to 0.97) for each additional calendar year of diagnosis, 4.38 (2.79 to 6.87) for grade III versus grade I tumors, 0.43 (0.31 to 0.62) for PR-positive versus PR-negative disease, and 2.01 (0.99 to 4.07) for HER2-positive versus HER2-negative disease. Women with grade III versus grade I tumors had a 56% increased risk of death from any cause (HR = 1.56%; 95% CI = 1.30 to 1.88%). Conclusion The risk of breast cancer death in T1abN0 disease continues to increase steadily beyond 10 years after diagnosis, has improved over time and varies substantially by tumor characteristics.