<h3>Background</h3> Immune checkpoint inhibitor therapy has a recognized role in oral squamous cell carcinoma (OSCC). Assessment of programmed death-ligand 1 (PD-L1) expression by immunohistochemistry by a trained histopathologist is the current standard method of stratifying patients for immunotherapy. However, to date, limited work has been undertaken on PD-L1 expression in oral dysplastic lesions (ODLs). <h3>Methods and Objective</h3> The principal aims of this study were to assess the expression of PD-L1 in ODL and OSCC using a clinically validated, companion diagnostic antibody (Dako 22C3 PharmDx) and to construct a comprehensive clinicopathologic database of OSCC and ODL. PD-L1 immunohistochemistry was assessed using the combined positive score (CPS) method by a trained histopathologist. In select cases, CD3 and CD8 expression were also assessed in lymphocytes. Statistical analysis was performed using Fisher exact and Pearson chi-square tests. <h3>Results</h3> The majority of OSCC cases tested were positive for PD-L1 using the CPS method (63%; 19/30). PD-L1 expression had a positive association with lymph node metastasis but this was not statistically significant (<i>P</i> > .05). In contrast, a smaller proportion of ODLs were positive for PD-L1 (20%; 4/20), all of which were severely dysplastic. Interestingly, PD-L1 in ODL expression was associated with the presence of a dense chronic inflammatory cell infiltrate. <h3>Conclusions</h3> Evaluating PD-L1 expression using CPS could identify patients with OSCC who may respond to immune checkpoint inhibitors. We have observed PD-L1 expression in a small number of severe ODLs, the significance of which is uncertain at present. Replication in larger patient cohorts is recommended for validation.