We report on 3-year-old Japanese twin brothers suffering from ictal vomiting during infancy. Intractable seizures, including generalized tonic-clonic convulsions, and myoclonic seizures persisted in late infancy. The diagnosis of severe myoclonic epilepsy in infancy was confirmed by detecting a mutation in the voltage-gated sodium channel alpha subunit type gene. This is the first case report addressing ictal vomiting as the initial presentation of severe myoclonic epilepsy in infancy.