Solitary primary bone lymphoma of the sacrum is rare. We report a case of a 77-year-old male patient who presented with unexplained numbness and pain in the right lower extremity for over 2 months. Tumor markers and other laboratory were unremarkable. Fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) revealed a solitary osteolytic bone lesion of the sacrum with intense 18F-FDG uptake (SUVmax=10.7). The subsequent biopsy confirmed the diagnosis of diffuse large B-cell lymphoma. After one cycle of R-CHOP, the neurological symptoms of the patient improved significantly.