Objective To elucidate current research status of immunoglobulin G4 (IgG4) and cancer immunity. Method The relevant literatures of relationship between IgG4 and cancer immunity were collected and reviewed. Results The IgG4 high-level and the intratumoral infiltration of the IgG4-positive plasma cells were the predictors for a worse prognosis in the cancer patients. The relationship between the serum IgG4 level and the prognosis in the cancer patients was unclear. The IgG4 related immunity might contribute to the tumor-associated escape from the immune surveillance. Conclusions Recent studies implicate that IgG4 might play a role in tumor progression. Specific mechanisms for IgG4 in tumor immune microenvironment need to be further explored. Dissecting relationship between IgG4 and cancer immunity might provide a novel idea for cancer therapy.