Abstract Objectives To determine life expectancy and causes of death after bariatric surgery in relation to baseline type 2 diabetes (T2D) in the prospective, Swedish Obese Subjects study. Methods The study included 2010 patients with obesity who underwent bariatric surgery and 2037 matched controls, eligible for surgery. The surgery group underwent gastric bypass (n = 265), banding (n = 376), or vertical banded gastroplasty (n = 1369). The control group (n = 2037) received usual obesity care. Causes of death were obtained from the Swedish Cause of Death Register, case sheets and autopsy reports, in patients with baseline T2D (n = 392 surgery patients/n = 305 controls) or non-T2D (n = 1609 surgery patients/n = 1726 controls) during a median follow-up 26 years. Results In T2D and non-T2D subgroups, bariatric surgery was associated with increased life expectancy (2.1, 95% confidence interval (95% CI) 0.2–4.0; and 1.6, 0.5–2.7 years, respectively) and reduced overall mortality (adjusted hazard ratio (adjHR) = 0.77, 95% CI: 0.61–0.97; and 0.82, 0.72–0.94, respectively), and the treatment benefit was similar (interaction p = 0.615). Bariatric surgery was associated with reduced cardiovascular mortality in both subgroups (adjHR = 0.65, 95% CI: 0.46–0.91; and 0.70, 0.55–0.88, respectively (interaction p = 0.516)). Conclusions Bariatric surgery is associated with similar reduction of overall and cardiovascular mortality and increased life expectancy regardless of baseline diabetes status.