With the introduction of many new treatments in multiple myeloma and the effective use of autologous stem cell transplantation, significant prolongation of overall survival has been achieved. Despite this ,there is still no cure for this disease. Relapses/refractory conditions seen after multiple treatments have brought the use of new agents to the agenda. Elranatamab is a humanized bispecific antibody used in relapsed or refractory multiple myeloma which targets B-cell maturation antigen on myeloma cells and CD3 on T cells . With this mechanism, elranatamab could activate T cells to induce cytotoxic T-cell response against myeloma cells. (1) Although we have an idea and experience about the short-term adverse effect profile and management, our ideas about the long-term adverse effect and safety profile are not yet clear due to the fact that it is a very new agent. We described an unexpected hematologic event during the use of elranatamab in the following case.