Anti-IgLON5 encephalitis was a rare neurological and heterogeneous disorder, which was mainly found in adults. Epileptic seizures related to anti-IgLON5 disease were rarely reported. Neural antibodies associated with autoimmune encephalitis in serum and cerebrospinal fluid (CSF) were tested using cell-based assays (CBA) with immunofluorescence double staining. The antibodies in serum were further confirmed by tissue-based assay (TBA) with rat brain and kidney tissue. We reported a pediatric case presented with epileptic seizures, cognitive impairments, and sleep disorders. Autoantibody screening showed anti-IgLON5 antibody IgG (1:100+) and anti-NMDAR antibody IgG (1:10+) in the serum. She was diagnosed as anti-IgLON5 encephalitis. Her conditions improved rapidly by treated with intravenous immunoglobulin and high dose intravenous methylprednisolone. We described the second pediatric case with anti-IgLON5 encephalitis, who was also the first presented with epileptic seizures as the initial presentation. Anti-IgLON5 encephalitis might have mild manifestations. For patients with new onset seizures associated with cognitive impairments and sleep disturbances, anti-IgLON5 antibody should be tested as early, even in children.