Abstract Background After radical cystectomy, patients are in a catabolic state because of postoperative stress response, extensive wound healing, and ileus. Objective To evaluate whether recovery can be improved with total parenteral nutrition (TPN) in patients following extended pelvic lymph node dissection (ePLND), cystectomy, and urinary diversion (UD). Design, setting, and participants We conducted a prospective, randomised, single-centre study of 157 consecutive cystectomy patients. Intervention Seventy-four patients (group A) received TPN during the first 5 postoperative days, with additional oral intake ad libitum. Eighty-three patients (group B) received oral nutrition alone. Outcome measurements and statistical analysis The primary outcome was the occurrence of postoperative complications. Secondary outcomes were time to recovery of bowel function, biochemical nutritional (serum albumin, serum prealbumin, serum total protein) and inflammatory (C-reactive protein) parameters, length of hospital stay, and costs attributed to the TPN. The Pearson χ2 test was used for dichotomous variables; the Wilcoxon rank sum test was used for continuous variables. Results and limitations Postoperative complications occurred in 51 patients (69%) in group A and in 41 patients (49%) in group B ( p = 0.013), a difference resulting from group A having more infectious complications than group B (32% vs 11%; p = 0.001). Serum prealbumin and serum total protein were significantly lower in group B on postoperative day 7 but not on postoperative day 12. Time to gastrointestinal recovery and length of hospital stay did not differ between the two groups. The costs for TPN were €614 per patient. A potential limitation is the use of a glucose-based parenteral nutrition without lipids. Conclusions Postoperative TPN is associated with a higher incidence of complications, mainly infections, and higher costs following ePLND, cystectomy, and UD versus oral nutrition alone.