Abstract: Gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) are neoplasms that develop from neuroendocrine cells and exhibit neuroendocrine functions. The lack of specific clinical symptoms and biological behaviors for NENs cause early misdiagnosis and missed diagnosis in a majority of cases. However, the molecular biology of GEP-NENs vary greatly in different primary sites and grades, contributing to the high heterogeneity in such type of tumors. Currently, the diagnosis of GEP-NENs mainly depends on traditional methods such as imaging and tissue biopsy, leading to imperfect diagnostics by only reflecting genetic information about the location of the biopsy sample in the overall neoplasm. With the rapid development of genome sequencing technology in recent years, the exploration of circulating biomarkers and liquid biopsy technology have compensated for the limitations of tissue biopsy, thereby creating new opportunities to improve the diagnostic rate of GEP-NENs and the realization of precise treatment. This review summarizes and compares the status of liquid biopsy applications in investigating GEP-NENs.