Programmed cell death‐ligand 1 (PD‐L1) is a transmembrane protein that acts as a co‐inhibitory factor in the immune response. Its receptor, programmed cell death protein 1 (PD‐1), is found on immune cells, where binding to PD‐L1 can reduce the proliferation of PD‐1‐positive cells, inhibit their cytokine secretion and induce apoptosis. PD‐L1 in immune‐privileged tissue plays a crucial role in peripheral tolerance. PD‐L1 can be overexpressed in various malignancies, including oral squamous cell carcinoma, where it can attenuate the host immune response to tumour cells and has been associated with a worse prognosis. Monoclonal antibody therapies targeting the PD‐1:PD‐L1 axis have shown initial promise, but further research is needed to identify which patients will benefit. We provide an update of knowledge on PD‐L1, including its structure, function and regulation. We also review studies on the overexpression of PD‐L1 in cancer, specifically oral squamous cell carcinoma, and explore its potential value as a therapeutic target.