A 34-year-old woman with hyperthyroidism, who had been previously treated with propylthiouracil (PTU) is reported. She was admitted because of clumsiness in her left hand and abnormal behavior. A neurological examination demonstrated impairment of higher cortical function, and weakness and hyperreflexia of the left leg. An MRI scan with gadolinium enhancement showed pachyleptomeningeal thickening in the right frontoparietal lobe. Blood tests revealed a high MPO-ANCA titer of 122 EU (normal:<10 EU). After steroid administration, the neurological symptoms and the MRI findings improved markedly. This is the first report of PTU-induced cerebral pachyleptomeningitis associated with a high serum MPO-ANCA titer.