B and T lymphocyte attenuator (BTLA) is an inhibitory immune checkpoint, which typically interacts with herpesvirus entry mediator (HVEM) and plays a crucial role in regulating immune balance. BTLA interacts with its ligand HVEM in a cis manner on the surface of the same immune cell to maintain immune tolerance, while trans interactions on the surface of different immune cells mediate immunosuppressive effects. Dysregulation of the BTLA/HVEM axis can impair the functions of immune cells, particularly T lymphocytes, promoting immune escape of tumor cells and ultimately leading to tumor progression. Researchers have found that BTLA and HVEM are abnormally expressed in various tumors and are associated with prognosis, suggesting that they may be potential targets for tumor immunotherapy. This review summarizes the molecular structures of BTLA and HVEM, immunomodulatory mechanisms, recent advances in hematologic malignancies, potential inhibitors of BTLA/HVEM interaction, and their applications in immunotherapy for hematologic malignancies.