Chronic GVHD is one of the major complications of BMT, involving a variety of organs, but rarely involving the genitourinary system. We report a patient who simultaneously developed extensive chronic GVHD and phimosis after BMT. From the clinical course and pathological findings, chronic GVHD was considered to be responsible for the phimosis. Despite intensive immunosuppressive therapy, the phimosis persisted. Phimosis is a rare complication after BMT, which may often remain neglected. Possibility of this complication should be considered in patients with chronic GVHD.