An interhemispheric lipoma is rare and is often associated with agenesis or hypogenesis of the corpus callosum. A 14-year-old girl who lost consciousness was brought to emergency room. It was stated that she had had a convulsion. During the neurologic examination, generalized tonic-clonic seizures were observed. Hypogenesis of the corpus callosum, interhemispheric and intraventricular lipomas, a single anterior cerebral artery, and mild hypoplasia in the cingulate gyri were observed on cerebral computed tomography and magnetic resonance imaging.