Epstein-Barr virus (EBV), a type of γ-herpes virus, is known to be a tumor virus. About 90% of adults were found to be persistently infected with EBV and this infection is responsible for Burkitt lymphoma (BL), extranodal NK/T cell lymphoma, Hodgkin lymphoma (HL), acquired Immune deficiency syndrome (AIDS)-associated lymphoma, and a portion of diffuse large B cell lymphomas (DLBCL). EBV-positive DLBCL in the elderly, a disease recognized in Japan, is described in the WHO classification as a new category of DLBCLs. Clinical studies of DLBCLs have since accumulated. We herein describe our clinicopathological study of EBV-positive DLBCL in the elderly in the rituximab era, and review EBV-positive B cell lymphoma cases. A potentially promising novel therapy for EBV-positive B cell lymphoma, anti-PD-1 antibody, is then introduced. Finally, we briefly discuss our unpublished study of EBV-positive B cell lymphoma and its microenvironment.