The objective of this retrospective cohort study was to evaluate mortality rate and cause of death after tonsil surgery in Sweden. Two national registries were used, both run by The Swedish National Board of Health and Welfare, an agency of the Ministry of Health and Social Affairs. In the National Patient register all tonsil surgeries performed in Sweden from 2004 through 2011 were identified. The result from this search was matched with the National Cause of Death Register to identify all deaths that occurred within 30 days of tonsil surgery. Personal identity numbers were used to do the matching of registers. Details on the cause of death were obtained from the Swedish National Board of Health and Welfare. Two deaths were identified in 82,527 operations. Both patients were male, otherwise healthy, children under the age of five, operated due to tonsil-related upper airway obstruction/snoring with coblation technique. Cause of death was bleeding-related airway obstruction in both cases and hemodynamic failure caused by blood loss. Both deaths occurred after discharge from the hospital within the first postoperative week. No abnormal levels of analgesics were found in the postmortal investigations. Two deaths related to tonsil surgery (performed on benign indications) were identified in 82,527 operations (2004-2011) in a well-defined national population. Both deaths were due to postoperative bleeding. Based on our findings, the frequency of post-tonsil-surgery mortality in Sweden was 1/41,263, 2004-2011. Level of evidence 2b retrospective cohort study.