We report a case of bone marrow infarction in a 20-year-old woman with acute lymphocytic leukemia (ALL) who underwent unrelated bone marrow transplantation (BMT). Hematopoietic engraftment occurred on day 9 and, thereafter, the patient developed acute dermal and hepatic graft-versus-host disease (GVHD). She also experienced severe arthralgia in her knee joints on day 21. Immunosuppressive therapy with prednisolone (PSL) for acute GVHD was given, and the arthralgia improved rapidly, correlating with the improvement in dermal and hepatic GVHD. Based on the laboratory findings and analysis of magnetic resonance images, she was diagnosed as having bone marrow infarction. The cause of the bone marrow infarction was thought to be acute GVHD-related microangiopathy.