This 15-year-old girl had subacute onset of secondary generalized seizures, confusion, and subsequent memory decline. MRI showed bilateral hippocampal swelling progressing to unilateral mesial temporal sclerosis (MTS) within 12 months. Epilepsy surgery was performed, and laboratory data were consistent with non-paraneoplastic limbic encephalitis. 18 months after epilepsy surgery, the patient is seizure-free with stable cognitive functions.