Diffuse large B-cell lymphoma (DLBCL) is a highly heterogeneous and aggressive hematologic malignancy that poses significant challenges in clinical practice due to its tendency for relapse and difficulty in achieving lasting remission. Tumor immunotherapy has shown considerable therapeutic potential for DLBCL by stimulating or reconstructing the body's immune system to recognize and eliminate tumor cells. The evolution of immunotherapy, from early monoclonal antibodies to bispecific/multispecific antibodies, chimeric antigen receptor (CAR) therapy, and more recently oncolytic viruses and gene therapies, has provided DLBCL patients with a broader range of treatment options. With ongoing research into the immunopathological mechanisms of DLBCL and its tumor microenvironment, new immunotherapies are expected to further enhance treatment efficacy and improve patient outcomes. This paper reviews the immunopathological mechanisms of DLBCL and the advancements in immunotherapy for this condition.