The patient was a 75-year-old man with a history of bronchial asthma. He visited our emergency outpatient department with chief complaints of sensory disturbance and weakness in both lower extremities, pain in the left lower extremity, and cough. Because the patient presented with neurological symptoms and a marked increase in peripheral eosinophil count, he was admitted to the hospital with a diagnosis of eosinophilic granulomatosis with polyangiitis (EGPA). Although the patient was treated with steroid pulse therapy, maintenance therapy with prednisolone (PSL), and high-dose intravenous immunoglobulin therapy for EGPA, neurological symptoms persisted at the time of hospital discharge. Mepolizumab was initiated on an outpatient basis; since then, the neurological symptoms have tended to improve, allowing the tapering of PSL to 2 mg. Neurological symptoms related to EGPA often persisted and directly led to a decline in activities of daily living. However, mepolizumab can be an effective treatment option for treatment-resistant neurological symptoms.