Immunotherapies targeting immune checkpoints have undergone rapid evolution, and have been preliminary explored in treatment of gastroenteropancreatic neuroendocrine neoplasm (GEP-NEN) in recent years. However, their potential to deliver tangible clinical benefits remains uncertain. In this article, we systematically reviewed the current status and efficacy of clinical trials, which evaluated immune checkpoint inhibitor (ICI) as monotherapy or in dual-ICI therapy for GEP-NEN. Despite lacking substantial breakthroughs in GEP-NEN treatment, ICI demonstrated some antitumor activity and safety in treating recurrent or metastatic GEP-NEN, albeit with a generally low objective response rate (ORR). The ORR of ICI in GEP-NEN treatment exhibited a negative correlation with tumor differentiation, suggesting that poorly diffe-rentiated gastroenteropancreatic neuroendocrine carcinoma (GEP-NEC) might achieve better clinical responses. Disease control rate of dual-ICI therapy was higher than that of monotherapy. However, dual-ICI also got more severe side effects. Given the rarity of mismatch repair gene defects and high microsatellite instability (dMMR/MSI-H) in GEP-NEN, patients with high tumor mutational burden (TMB-H≥10 muts/Mb) could get potentially benefit from ICI therapy. In the future, it is expected to further explore the synergistic combined application of ICI with chemotherapy, radiotherapy, and antiangiogenic drugs in GEP-NEN, which may enhance its antitumor efficacy. Clinically, the benefit groups of ICI immunotherapy should be evaluated comprehensively according to pathological grading, immune markers, disease progression, and patient's physical condition.