Perioperative dexamethasone is associated with attenuation of the postoperative systemic inflammatory response and fewer postoperative complications following elective surgery for colorectal cancer. This study examined the impact of different doses of dexamethasone, given to reduce postoperative nausea and vomiting (PONV) after elective colonic resection for cancer, on the postoperative Glasgow Prognostic Score (poGPS) and morbidity.Patients from a single centre were included if they underwent potentially curative resection of colonic cancer from 2008 to 2017 (n = 480). Patients received no dexamethasone (209, 44%), or either 4 mg (166, 35%), or 8 mg (105, 21%), intravenously during anaesthesia, at the discretion of the anaesthetist. The postoperative Glasgow Prognostic Score (poGPS) on day 3 and 4, and complication rate at discharge were recorded.When patients were grouped by surgical approach (open or laparoscopic) and dexamethasone dose (0 mg, 4 mg or 8 mg), there was a statistically significant linear trend toward a lower postoperative systemic inflammatory response (day 3 poGPS) with the use of minimally invasive surgery and higher doses of dexamethasone (p < 0.001). Furthermore, this combination of laparoscopic surgery and higher doses of dexamethasone was significantly associated with a lower proportion of postoperative complications (p < 0.001). At multivariate Cox regression, dexamethasone was not significantly associated with either improved or poorer cancer specific or overall survival.Higher doses of perioperative dexamethasone are associated with greater reduction in postoperative systemic inflammation and complications following surgery for colonic cancer without negative impact on survival.