Abstract: Tumor cells exploit immune checkpoint pathways to evade the host immune system and suppress immune cell function. Cancer cells express programmed death-ligand 1/2 (PD-L1/PD-L2) and bind to programmed cell death protein-1 (PD-1) present on cytotoxic T cells, triggering inhibitory signal transduction and reducing cellular toxicity and T cell exhaustion. Targeting the PD-1 pathway significantly enhances the cytotoxic activity of T cells, thereby inducing tumor cell lysis. Immune checkpoint blockade can suppress this signal, rendering it an effective treatment strategy for cancer patients. In recent years, we have witnessed unprecedented clinical efficacy of immunotherapies involving PD-1 or PD-L1 blockade in treating advanced cancers, including hematologic malignancies, supporting the essential roles of PD-1 and PD-L1 in immune suppression. This article reviews clinical research into PD-1/PD-L1–related pathway drugs in lymphoma.