In this systematic review and meta-analysis, 25 clinical trials were systematically reviewed, and meta-analysis was performed with the results of 16 trials. It was found that the risk of surgical site infection was significantly lower in patients who received perioperative immunonutrition than those given standard nutrition. Furthermore, hospital stay was significantly shorter in patients receiving immunonutrition or early enteral nutrition after surgical resection of gastric cancer. Perioperative immunonutrition also significantly reduced white blood cell counts and the level of C-reactive protein in the patients. However, neither CD4+ T cells nor inflammatory cytokines were significantly affected even though immunonutrition was in favor. These findings suggested that patients with gastrointestinal cancer may benefit from perioperative immunonutrition support by reducing surgery-associated complications and shortening hospital stay. The effects and the underlying mechanism of immunonutrition on immunological modulation and inflammatory regulation, however, remain to be further defined.