Mutations in SCN8A, which codes for the voltage-gated sodium channel NaV1.6, have been described in relation to infantile onset epilepsy with developmental delay and cognitive impairment. Here, we report the case of an infant and her father with early onset benign familial infantile epilepsy, but without cognitive or neurological impairment. In this patient, diagnostic exome sequencing (DES) identified a heterozygous mutation (c.4427G>A; p.Gly1476Asp) in the SCN8A gene. This mutation, confirmed by Sanger sequencing, effects a highly conserved amino acid. In-silico analysis predicts that this mutation may be pathogenic. To our knowledge, this is the first clinical report on Korean benign familial infantile epilepsy with a SCN8A mutation. We were able to achieve good seizure control in our patients with sodium channel blockers. This result suggests the application of DES will be valuable for the diagnosis of patients with infantile epilepsy but no cognitive impairment.