High-risk surgery is performed in every acute hospital. These patients often have increased peri-operative risk related to their poor cardiorespiratory reserve. Formal risk assessment is recommended for such patients; cardiopulmonary exercise testing is a well established triage tool, but is unavailable in many hospitals. We investigated whether a simple exercise test could predict postoperative outcome using a prospective trial of 121 patients undergoing elective major abdominal surgery. Each patient completed a shuttle walk test and was followed up for 30 days after surgery. There was one postoperative death (0.8%), with 53 patients (44%) developing complications. The mean (SD) shuttle walk test distance was significantly different between patients who suffered complications and those who did not (276.6 (134.5) vs 389.6 (138.9) m, respectively; p < 0.001). A cut-off distance of 250 m had a specificity of 0.88 and a sensitivity of 0.58 to predict postoperative complications. Patients unable to complete a shuttle walk test above this cut-off distance were three times more likely to have a postoperative morbidity. We conclude that the shuttle walk test can help identify patients who are at increased peri-operative risk.