<b><i>Background:</i></b> Complications after major abdominal surgery (MAS) are associated with increased morbidity and mortality. Rising costs in health care are of increasing interest and a major factor affecting hospital costs are postoperative complications. In this study, the costs associated with complications are assessed. <b><i>Methods:</i></b> Retrospective cohort study of 399 consecutive patients that underwent MAS. Analysis of total costs for hospital stay, complications and treatment was performed, including bootstrapping; allowing for subtraction of data with 95% confidence intervals. <b><i>Results:</i></b> For a single patient who underwent MAS the average costs, adjusted for ASA-classification and surgery type, adds up to EUR 8,584.81 (95% CI EUR 8,332.51 - EUR 8,860.81) in patients without complications. EUR 15,412.96 (95% CI EUR 14,250.22 - EUR 16,708.82) after minor complications, and EUR 29,198.23 (95% CI EUR 27,187.13 - EUR 31,295.78) after major complications (p < 0.001). <b><i>Conclusion:</i></b> The results provide an insight into the scope of hospital costs associated with complications. Major complications occur in 20% of patients undergoing MAS and account for 50% of the total costs of care. Implementation of a protocol aimed at early diagnosis and treatment of complications might lead to a decrease in morbidity and mortality, but also prove to be cost effective.