Congenital fiber type disproportion (CFTD) is a rare form of congenital myopathy characterized by the smallness and the marked predominance of type 1 fibers, which presents congenital hypotonia, delayed motor milestones, joint contractures, and skeletal deformities. The muscle biopsy reveals the type 1 fibers are more than 12% smaller than the type 2 fibers in size. We describe a 24-month-old boy who presented muscle hypotonia, delayed motor milestones, mental retardation with generalized tonic clonic seizures, and the muscle pathologic findings of CFTD. Additional findings included left cryptorchidism, congenital subluxation of the hip, contractures of ankle joints, diffuse brain atrophy, and optic nerve atrophy. We should consider CFTD as a differential diagnosis of early onset myopathy.