Concurrent extramedullary infiltration in multiple organs is uncommon in adults with acute lymphoblastic leukemia. A 21-year-old woman who presented fatigue had a new diagnosis of acute lymphoblastic leukemia underwent FDG PET/CT. The images demonstrated extramedullary infiltration in multiple organs, including the liver, pancreas, kidney and the bone. However, no clinical signs or laboratory tests were suggestive of the involvement of these organs. After four cycles of chemotherapy, the patient’s symptoms were relieved and all previously visualized abnormal activity disappeared on the follow-up FDG PET/CT.