Cerebellar research has focused principally on adult motor function. However, the cerebellum also maintains abundant connections with nonmotor brain regions throughout postnatal life. Here we review evidence that the cerebellum may guide the maturation of remote nonmotor neural circuitry and influence cognitive development, with a focus on its relationship with autism. Specific cerebellar zones influence neocortical substrates for social interaction, and we propose that sensitive-period disruption of such internal brain communication can account for autism’s key features. Although the cerebellum is usually considered a motor structure, it also maintains connections with nonmotor brain regions throughout life. Wang et al. propose that the cerebellum guides sensitive-period maturation of remote neural circuitry, and focus on its relationship with autism.