To assess clinical efficacy of using postoperative branched-chain amino acids (BCAAs)-enriched nutritional support in lower gastrointestinal cancer patients, we conducted a retrospective observational study comparing this regimen with traditional fluid management. Sixty-one eligible colorectal cancer patients consecutively admitted in the Colorectal Surgery Ward to receive postoperative hypocaloric peripheral parenteral nutrition (HPPN) were categorized into dextrose-only control group (n = 20), dextrose plus low-dose BCAA fat group (n = 20), and dextrose plus high-dose BCAA fat group (n = 21). Nutritional, clinical, and biochemical outcomes were collected on the day before and 7 days after surgery. Patients were nonmalnourished. Over the 7-day observation period, the control group had a significantly higher reduction in body mass index than the lower dose and the higher dose BCAA groups (P = 0.023 and P = 0.002, respectively). Compared to high-dose BCAA group, the control group also had a lower nitrogen excretion (P < 0.0001) and less reduction in nitrogen balance (P < 0.0001). There were no differences between study groups in biochemical measures, phlebitis, postoperative hospital stay, and in-hospital mortality. We found no better clinical advantage to the postoperative administration of BCAA-enriched HPPN than fluid management in nonmalnourished colorectal cancer patients.