Purpose: A defunctioning stoma reduces the risk of symptomatic anastomotic leakage after low anterior resection for rectal cancer and mitigates the consequences when a leakage occurs, but the impact on mortality and oncological outcomes is unclear. The aim was to investigate the associations of a defunctioning stoma with short- and long-term outcomes in patients undergoing low anterior resection for rectal cancer. Methods: Data from all patients who underwent curative low anterior resection for rectal cancer between 1995 and 2010 were obtained from the Swedish Colorectal Cancer Register. A total of 4130 patients, including 2563 with and 1567 without a defunctioning stoma, were studied. Flexible parametric models were used to estimate hazard ratios for all-cause mortality, 5-year local recurrence, and distant metastatic disease in relation to the use of defunctioning stoma, adjusting for confounding factors and accounting for potential time-dependent effects. Results: During a median follow-up of 8.3 years, a total of 2169 patients died. In multivariable analysis, a relative reduction in mortality was observed up to 6 months after surgery (hazard ratio = 0.82: 95% CI 0.67–0.99), but not thereafter. After 5 years of follow-up, 4.2% (173/4130) of the patients had a local recurrence registered and 17.9% (741/4130) had developed distant metastatic disease, without difference between patients with and without defunctioning stoma. Conclusion: A defunctioning stoma is associated with a short-term reduction in all-cause mortality in patients undergoing low anterior resection for rectal cancer without any difference in long-term mortality and oncological outcomes, and should be considered as standard of care. [ABSTRACT FROM AUTHOR]