Gastroenteropancreatic neuroendocrine neoplasms are a rare, heterogeneous group of neoplasms. The incidence has increased greatly during the past 40 years, partially due to the advanced endoscopic and imaging techniques. As a type of neoplasm with the specific morphology and immunophenotype, its nomenclature and classification have also been changed considerably over the past 40 years, from the past "carcinoid" to the current "neuroendocrine neoplasm". WHO currently recommends two-tiered classification, neuroendocrine tumors and neuroendocrine cancer, according to the differentiation, morphology and proliferation index. However, the neoplasms from different sites have different phenotypes, biological behaviors, and accordingly the different staging systems for the indication on prognosis and therapy selection. Recent research indicates that the tumor from different sites could express different molecular markers which are useful for the further study of molecular features, as well as the evaluation of the site of primary tumor. Along with the progress of the research on molecular mechanisms, including signal transduction, epigenetics and tumor microenviroment, the mode of diagnosis and treatment would also be changed accordingly. In this article, new advances in classification, clinical and pathological features and molecular mechanism of gastroenteropancreatic neuroendocrine neoplasms will be reviewed.