B7H3 is a transmembrane protein that belongs to the B7 family of immune checkpoint proteins. The B7 family consists of activating and inhibitory co-stimulatory molecules that positively and negatively regulate immune responses and are emerging key players in human cancer. An imbalance in immune regulation profoundly affects tumor-specific T-cell immunity in the cancer microenvironment and can reshape tumor progression, metastasis and immunotherapy in patients with cancer. B7H3 is overexpressed in a variety of tumor types, in correlation with poor prognosis. Therefore, B7H3 is a promising immunotherapy target and a potential biomarker.