Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is a rare autoimmune disorder manifesting as seizures, movement disorders, and psychiatric changes. However, there have been few case reports concerning this disorder in South Korean children. The current case report describes a pediatric patient with anti-NMDAR encephalitis. A 13-year-old female patient developed clonic movements of the right arm followed by aphasia, paresthesia, and right-sided hemiparesis. The electroencephalogram (EEG) results indicated electroclinical seizures arising from the left temporal area. Brain magnetic resonance imaging (MRI) revealed high signal intensity and cortical swelling in left temporal lobe. Anti-NMDAR antibodies were detected in the cerebrospinal fluid (CSF). The patient was treated with intravenous immunoglobulin and high-dose methylprednisolone and showed partial improvement in language skills, paresthesia, and motor power. The brain MRI and EEG results also indicated improvement. However, anti-NMDAR antibodies persisted in the CSF. After four doses of rituximab, the patient exhibited complete recovery of language and motor skills, and was seizure free under treatment with antiepileptic medication. There were no residual anti-NMDAR antibodies in the CSF at her 24-month follow-up visit. This case report elucidates the benefits of early intervention using rituximab to improve neurological deficits and achieve baseline recovery in patients with anti-NMDAR encephalitis.