Posttranslational modifications (PTM) of PD-L1 have emerged as important regulatory mechanisms that modulate immunosuppression in patients with cancer. In exposure to inflammatory cytokines, cancer cells and antigen-presenting cells, such as macrophages and dendritic cells, express PD-L1 to inhibit the activity of effector T cells through PD-1 engagement. Recent studies suggested that glycosylation, phosphorylation, ubiquitination, sumoylation, and acetylation play important roles in the regulation of PD-L1 protein stability and translocation and protein–protein interactions. Aberrant alterations of PTMs directly influence PD-L1–mediated immune resistance. On the basis of the newly identified regulatory signaling pathways of PD-L1 PTMs, researchers have investigated the cancer therapeutic potential of natural food compounds, small-molecule inhibitors, and mAbs by targeting PD-L1 PTMs. Results of these preclinical studies demonstrated that targeting PTMs of PD-L1 yields promising antitumor effects and that clinical translation of these therapeutic strategies is warranted. Cancer Res; 78(22); 6349–53. ©2018 AACR.