Low-grade epilepsy-associated tumors (LEAT) are brain tumors that should be differentiated as a cause of symptomatic epilepsy in children. The most common initial symptom is epileptic seizure, particularly focal seizures. We present a case of LEAT in which an infant presented to our department with convulsive-like seizures that were observed from approximately 3 months of age. At the first visit, growth and development, including head circumference, were appropriate for age. The seizures were atypical, but ictal video electroencephalography showed abnormal waves indicative of left hemispheric epilepsy. The patient subsequently presented with somnolence and poor feeding, and a sudden increase in head circumference and hydrocephalus were observed. Thus, the patient was urgently admitted to the neurosurgery department of our hospital. Brain MRI showed a suspected brain tumor and elective craniotomy was performed. No epileptic seizures were observed postoperatively. When focal epileptic seizures are observed in infancy, a brain tumor should also be considered as a differential diagnosis, and further examination may be warranted.