Post-translational modifications (PTMs) of PD-1, including glycosylation, phosphorylation, ubiquitination, and palmitoylation, play critical roles in regulating PD-1 stability, localization, and interactions. These modifications are essential for modulating immune responses and have emerged as potential targets for enhancing cancer immunotherapy. PD-1 is expressed on various immune cells, including T cells, B cells, and myeloid cells, and its expression is tightly regulated by transcriptional and epigenetic mechanisms. In cancer, PD-1 can have dual roles, either promoting or suppressing tumor progression depending on the context. Targeting PD-1 PTMs offers a promising strategy to enhance the efficacy of immune checkpoint inhibitors. Glycosylation of PD-1 is particularly important, as it influences PD-1-PD-L1 interactions and T-cell activity. Glycosylated PD-1 can be targeted with specific antibodies to enhance antitumor immunity. Phosphorylation of PD-1, particularly at tyrosine and serine residues, regulates its function and interaction with SHP-2, which modulates T-cell signaling. Ubiquitination and deubiquitination of PD-1 also play key roles in its stability and degradation. Palmitoylation of PD-1 affects its subcellular localization and stability. Therapeutic strategies targeting PD-1 PTMs include inhibitors of glycosyltransferases, SHP-2 activators, and PROTACs that promote PD-1 degradation. These approaches aim to enhance T-cell activity and improve the response to immunotherapy. Understanding PD-1 PTMs is crucial for developing more effective cancer immunotherapies.Post-translational modifications (PTMs) of PD-1, including glycosylation, phosphorylation, ubiquitination, and palmitoylation, play critical roles in regulating PD-1 stability, localization, and interactions. These modifications are essential for modulating immune responses and have emerged as potential targets for enhancing cancer immunotherapy. PD-1 is expressed on various immune cells, including T cells, B cells, and myeloid cells, and its expression is tightly regulated by transcriptional and epigenetic mechanisms. In cancer, PD-1 can have dual roles, either promoting or suppressing tumor progression depending on the context. Targeting PD-1 PTMs offers a promising strategy to enhance the efficacy of immune checkpoint inhibitors. Glycosylation of PD-1 is particularly important, as it influences PD-1-PD-L1 interactions and T-cell activity. Glycosylated PD-1 can be targeted with specific antibodies to enhance antitumor immunity. Phosphorylation of PD-1, particularly at tyrosine and serine residues, regulates its function and interaction with SHP-2, which modulates T-cell signaling. Ubiquitination and deubiquitination of PD-1 also play key roles in its stability and degradation. Palmitoylation of PD-1 affects its subcellular localization and stability. Therapeutic strategies targeting PD-1 PTMs include inhibitors of glycosyltransferases, SHP-2 activators, and PROTACs that promote PD-1 degradation. These approaches aim to enhance T-cell activity and improve the response to immunotherapy. Understanding PD-1 PTMs is crucial for developing more effective cancer immunotherapies.