Sweet disease is a multisystem inflammatory disorder characterized by fever, cutaneous erythematous plaques, and aseptic neutrophilic infiltration of various organs. Neuro-Sweet disease is a known rare central nervous system complication of Sweet disease. A 67-year-old Japanese woman who was diagnosed with neuro-Sweet disease underwent C-methionine (C-MET) PET. C-MET PET revealed increased accumulation in the affected brain tissues. After steroid therapy, she became asymptomatic, and a follow-up C-MET PET scan showed disappearance of the abnormal uptake of C-MET.