Nephrotic syndrome (NS) is a rare complication of allogeneic hematopoietic stem cell transplantation (allo-HSCT). The cases of 2 patients who developed NS after receiving allo-HSCT for chronic myelogenous leukemia and acute lymphoblastic leukemia are described. In both cases, renal biopsy revealed membranous nephropathy (MN), and the patients achieved remission after treatment with prednisolone. Previously reported cases and our experience suggest that most NS patients show MN in histologic tests after allo-HSCT and that its development is related to graft-versus-host disease. Early treatment with steroids seems effective for resolving symptoms of NS and improving renal function.