Major gastrointestinal surgery is associated with immune suppression and a high risk of postoperative complications. The aim of this open, randomized controlled trial was to examine the effect of supplementary per oral immunonutrition (IN) seven days before surgery for pancreatic cancer (PC) on postoperative complications and length of hospital stay (LOS). Secondary outcomes were the changes in functional capability and body weight (BW). Consecutive patients referred for surgery for diagnosed or plausible PC were included. The patients in the intervention group received supplementary IN (Oral Impact®, Nestlé) to reach a goal of 1.5 g protein/kg BW. The control group continued their habitual diet. Complications and LOS were independently assessed by the surgical staff. Secondary outcomes were measured 10, 20, and 30 days postoperatively. Thirty-five patients were included, of whom 19 (54%) were allocated to the intervention group. The doses of IN ranged from 250 to 1000 ml per day and the median compliance was 100 (0-100%). Based on the principle of intention-to-treat, no significant differences were found between the groups. We conclude that the lack of effect could be due to the limited dosage of IN, and/or because only 40% of the patients were at nutritional risk.