New Zealand has a high incidence of colorectal cancer. Most patients are treated with resectional surgery. There is a significant rate of complication associated with treatment. Costs of surgical treatment and effect of complications have not been previously investigated in New Zealand. The aim of this study was to define treatment costs of complications in patients undergoing resectional surgery for colorectal cancer.Adult patients who underwent a resectional operation for colorectal adenocarcinoma at Northland DHB between January 2011 and December 2016 were identified. Actual costs and diagnoses-related group (DRG) costs were obtained. Demographic data and information on outcomes were identified using the hospital's results reporting system CONCERTO.Three hundred and ninety patients were included. One hundred and seven patients suffered a complication. Median cost per patient was $17,090. In those with complications, median cost was $28,485 compared to $14,697 in those without. Cost of complications increased as complication grade increased. Additional cost in patients with complications was on average $20,683 per patient, equating to a total of $2.2 million in this cohort.This study has defined the costs associated with colorectal cancer resection. Complications following colorectal surgery add significant costs. Significant investment in initiatives to reduce complications is justified.