Mutations in the protocadherin 19 gene (PCDH19) are associated with a female-restricted form of epilepsy. As the disorder has an X-reversed inheritance pattern, men are usually healthy carriers. PCDH19 epilepsy among men due to mosaicism is rare but probably underdiagnosed. We describe the longitudinal development of the behavioral and neuropsychological profile of a male with a mosaic PCDH19 mutation based on assessments carried out at 9, 11, 15, and 19 years of age. He was diagnosed with mild intellectual disability and autism spectrum disorder and had marked deficits in so-called hot executive functions related to emotion, as opposed to purely cognitive aspects of executive functions, the so-called cold executive functions. Although his epilepsy improved and cognition remained stable, executive dysfunction and behavioral problems became the prominent clinical features with age.