Abstract Background After major upper gastro-intestinal surgery, enteral feeding is often hampered. There is still no consensus on which route of nutrition is preferable in patients undergoing this type of surgery. Current ESPEN guidelines recommend parenteral nutrition in undernourished patients, if caloric requirements cannot be met orally/enterally within 7 days and enteral nutrition is contraindicated. Objective The current practice of systematic parenteral nutrition at the thoracic surgery ward of the University Hospitals Leuven was evaluated based on the ESPEN guidelines. Method This prospective observational study included patients undergoing upper gastro-intestinal surgery and receiving postoperative parenteral nutrition. Parenteral nutrition use was considered appropriate when patients were undernourished and unable to obtain adequate caloric requirements by oral or enteral feeding within 7 days. Results Twenty-five out of 35 patients were nutritionally at risk. In 9 of 25 patients, the indication for parenteral nutrition was considered justified. As the intestinal tract below the anastomosis site remains accessible in the total studied population, enteral nutrition might be an option. Unfortunately, an appropriate jejunostomy tube was not available at our institution. Conclusion In accordance to the ESPEN guidelines, enteral nutrition can replace parenteral nutrition in most thoracic surgery patients, but only if an appropriate enteral access is available