Background: Patients undergoing abdominal surgery for solid tumours frequently develop major postoperative complications, which negatively affect quality of life, costs of care and survival. Few studies have identified the determinants of perioperative complications in this group. Methods: We performed a prospective observational study including all patients (age > 18) undergoing abdominal surgery for cancer at a single institution between June 2011 and August 2013. Patients undergoing emergency surgery, palliative procedures, or participating in other studies were excluded. Primary outcome was a composite of 30-day all-cause mortality and infectious, cardiovascular, respiratory, neurologic, renal and surgical complications. Univariate and multiple logistic regression analyses were performed to identify predictive factors for major perioperative adverse events. Results: Of a total 308 included patients, 106 (34.4%) developed a major complication during the 30-day follow-up period. Independent predictors of postoperative major complications were: age (odds ratio [OR] 1.03 [95% CI 1.01-1.06] , p=0.012 per year), ASA (American Society of Anesthesiologists) physical status greater than or equal to 3 (OR 2.61 [95% CI 1.33-5.17], p=0.003), a preoperative haemoglobin level lower than 12g/dL (OR 2.13 [95% CI 1.21-4.07] , p=0.014), intraoperative use of colloids (OR 1.89, [95% CI 1.03-4.07], p=0.047), total amount of intravenous fluids (OR 1.22 [95% CI 0.98-1.59] , p=0.106 per litre), intraoperative blood losses greater than 500mL (2.07 [95% CI 1.00-4.31], p=0.043), and hypotension needing vasopressor support (OR 4.68 [95% CI 1.55-27.72] , p=0.004). The model had good discrimination with the area under the ROC curve being 0.80 (95% CI 0.75-0.84, p <0.001). Conclusions: Our findings suggest that a perioperative strategy aimed at reducing perioperative complications in cancer surgery should include treatment of preoperative anaemia and an optimal fluid strategy, avoiding fluid overloa d and intraoperative use of colloids. © 2018 The Author(s).