We report the case of 13-year-old boy who had been diagnosed as having anaplastic large cell lymphoma (ALCL) when he was 11 years old. He suffered a relapse despite the chemotherapy regimens he had been subjected to. Since anaplastic lymphoma kinase (ALK), one of the important prognostic factors of ALCL, was not expressed in the tumor cells, allogeneic peripheral blood stem cell transplantation (PBSCT) from his HLA-matched elder brother was performed. Eleven months after PBSCT, the patient developed nephrotic syndrome as a consequence of chronic graft-versus-host disease (GVHD). He was diagnosed as having membranous nephropathy (MN) based on the results of histological examinations. Soluble interleukin-2 receptor and anti-nuclear antibody closely reflected the clinical course of MN, therefore some immune mechanisms closely related to chronic GVHD seemed to contribute to the occurrence of MN after PBSCT.