Background: Resection quality after robot-assisted surgery for colorectal cancer have not previously been investigated in a nationwide study. The aim of the study was to examine the resection quality in robot-assisted versus laparoscopic surgery for colorectal cancer. Furthermore, 30-day mortality, postoperative complications, and conversion to open surgery were investigated. Methods: Patients undergoing either laparoscopic or robot-assisted surgery for colorectal cancer between 1 January 2010 and 31 December 2015 were included. The primary outcome was whether R0 resection was achieved. Secondary outcomes were 30-day mortality, postoperative complications, and conversions to laparotomy. Results: A total of 8615 and 3934 patients had a diagnosis of colon cancer and rectal cancer respectively. Of the patients with colon cancer, 511 patients underwent robot-assisted surgery and of the patients with rectal cancer, 706 patients underwent robot-assisted surgery. In the multivariate analysis, patients with colon cancer had an odds ratio (OR) = 0.63 (95%CI 0.45–0.88) for receiving R0 resection in the robot-assisted group compared to laparoscopy. For patients with rectal cancer, the OR was 1.20 (95%CI 0.89–1.61). No difference in 30-day mortality or postoperative complications were observed. The OR of conversion to laparotomy was lower in the robot-assisted group compared to the laparoscopic group in both patients with colon – and rectal cancer. Conclusions: The study showed significant lower odds of receiving R0 resection in patients with colon cancer undergoing robot-assisted surgery. In patients with rectal cancer the robot-assisted surgery non-significantly increased the odds of receiving R0 resection.