The effects of nutritional support on well-nourished patients have been investigated, but the results were inconsistent among different articles. We performed the meta-analysis to examine the existing evidence. We systematically retrieved articles from PubMed, Web of Science and the Cochrane Library to identify the evidence of nutritional support for well-nourished patients. Methodological quality assessment was assessed based on the Cochrane Handbook and GRADE. Nine randomized controlled trials (RCTs) and one non-RCT with 1400 participants were included in this meta-analysis. Nutritional support, particularly immunonutrition, was associated with a significant reduction in postoperative infectious complications (OR = 0.74, 95% CI: 0.57-0.96), and a decreasing trends in morbidity and the length of the hospital stay (LOS) were observed. However, the mortality rates were comparable between two groups. The quality of evidence was moderate to high. Nutritional support, particularly immunonutrition supplementation, is likely to reduce infectious complications, morbidity and LOS without influencing mortality and may be a safe and preferred choice for well-nourished patients undergoing surgery for cancer. However, additional RCTs are warranted to determine the effects of nutritional support on well-nourished patients.