Objectives Later weekday of surgery for oesophageal cancer seems to increase 5-year mortality, but the mechanisms are unclear. We hypothesised that early postoperative reoperations and mortality might explain this association, since reoperation after oesophagectomy decreases long-term prognosis, and later weekday of elective surgery increases 30-day mortality.

Design This was a population-based cohort study during the study period 1987–2014.

Setting All Swedish hospitals conducting elective surgery for oesophageal cancer in Sweden.

Participants Included were 1748 patients, representing almost all (98%) patients who underwent elective surgery for oesophageal cancer in Sweden during 1987–2010, with follow-up until 2014.

Primary and secondary outcome measures The risk of reoperation or mortality within 30 days of oesophageal cancer surgery was assessed in relation to weekday of surgery by calculating ORs with 95% CIs using multivariable logistic regression. ORs were adjusted for age, comorbidity, tumour stage, histology, neoadjuvant therapy and surgeon volume.

Results Surgery Wednesday to Friday did not increase the risk of reoperation or mortality compared with surgery Monday to Tuesday (OR=0.99, 95% CI 0.75 to 1.31). A decreased point estimate of reoperation (OR=0.88, 95% CI 0.64 to 1.21) was counteracted by an increased point estimate of mortality (OR=1.28, 95% CI 0.83 to 1.99). ORs did not increase from Monday to Friday when each weekday was analysed separately. There was no association between weekday of surgery and reoperation specifically for anastomotic leak, laparotomy or wound infection. Stratification for surgeon volume did not reveal any clear associations between weekday of surgery and risk of 30-day reoperation or mortality.

Conclusions Weekday of oesophageal cancer surgery does not seem to influence the risk of reoperation or mortality within 30 days of surgery, and thus cannot explain the association between weekday of surgery and long-term prognosis.