Eosinophilic meningoencephalitis is a rare inflammatory condition of the central nervous system. As a limited number of cases has been reported, debate remains on the optimal treatment. We present a case of idiopathic eosinophilic meningoencephalitis successfully treated with glucocorticoids and intravenous immunoglobulin (IVIG). After extensive evaluation to rule out other possible causes, the patient was treated with intravenous (IV) dexamethasone and showed significant improvement within a few days. However, neurologic impairment persisted, and follow-up lumbar puncture results showed only a mild decrease in pleocytosis. Even after an additional 5 days of IV methylprednisolone, cerebrospinal fluid (CSF) pleocytosis persisted, and brain magnetic resonance imaging (MRI) showed an increase in enhanced lesions, implying persistent neuroinflammation. The patient was maintained on high-dose oral prednisolone for 2 months, and additional immune-modulatory effects were treated with IVIG. Follow-up MRI at 2 months showed a significant decrease in the extent of multiple enhanced lesions and a normalized CSF profile. The patient was maintained on regular maintenance doses of IVIG for an additional 6 months without any neurologic signs or symptoms. Inflammation is the key pathophysiology underlying neurological damage in eosinophilic meningoencephalitis. A literature review revealed that corticosteroid treatment is the only anti-inflammatory treatment used in cases of idiopathic meningoencephalitis, resulting in sufficient response in most patients but only partial response or death in a few cases. This is the first case report of IVIG use in idiopathic eosinophilic meningoencephalitis, suggesting the possibility of a new treatment modality for refractory cases.