The effect of early isoenergetic feeding routes [early enteral nutrition (E-EN) or early supplemental parenteral nutrition (E-SPN)] on the outcome of patients undergoing major abdominal surgery is controversial.The aim of this study was to investigate the impact of early isoenergetic EN compared with early isoenergetic SPN on nosocomial infections in patients undergoing major abdominal surgery.This study is a secondary, post hoc analysis of data from 2 open-label randomized clinical trials. Participants were recruited from the general surgery department of 11 academic hospitals in China undergoing major abdominal surgery and with Nutritional Risk Screening 2002 score ≥3. All eligible patients were categorized into 2 groups based on their achievement of the 100% energy target on postoperative day (POD) 3: the E-EN group (n = 199) and the E-SPN group (n = 115). The primary outcome was the incidence of nosocomial infections between POD 3 and hospital discharge.In total, 314 patients [mean (SD) age, 59.2 (11.4) y; 113 (36.0%) females] were included. Patients in the E-EN group showed no significant difference in nosocomial infections compared with those in the E-SPN group {17/199 [8.5%] compared with 10/115 [8.7%], risk difference, 0.2% [95% confidence interval (CI): -6.3, 6.6]}. The hematological nutritional status of the E-EN group showed a significant improvement at discharge compared with the E-SPN group (albumin: 38.0 ± 6.0 g/L compared with 35.5 ± 7.6 g/L; mean difference, -2.5 g/L; 95% CI: -4.0, -1.0 g/L; prealbumin: 200.0 ± 8.0 mg/L compared with 158.4 ± 38.1 mg/L; mean difference, -41.6 mg/L; 95% CI: -41.7, -36.1 mg/L). Other indicators were comparable between groups.E-EN compared with isoenergetic SPN may not be associated with a reduced rate of nosocomial infection in patients undergoing major abdominal surgery, but may be associated with improved hematological nutritional status.This trial was registered at clinicaltrials.gov as NCT03115957 (https://clinicaltrials.gov/ct2/show/NCT03115957) and NCT03117348 (https://clinicaltrials.gov/ct2/show/NCT03117348).Copyright © 2024 American Society for Nutrition. Published by Elsevier Inc. All rights reserved.