To clarify the involvement of the cerebellum in impaired sensory integration in patients with schizophrenia, 52 first-episode patients with schizophrenia and 52 age- and sex-matched healthy controls underwent a verified sensory integration imaging task to examine the whole-brain dysfunction underlying impaired sensory integration. The familiality of cerebellar activation when integrating sensory stimuli was investigated in 25 siblings of the patients with schizophrenia, while the heritability of cerebellar activation was estimated in 56 monozygotic twins and 56 dizygotic twins. In addition, the functional connectivity between the cerebellum and the remaining regions of the whole brain was explored with psychophysiological interaction analysis. Relative to healthy controls, patients with schizophrenia showed reduced cerebellar activation when performing the sensory integration task in the whole-brain analysis. This reduced cerebellar activation was also found in the siblings of patients with schizophrenia. but to a lesser extent compared with schizophrenia patients. Cerebellar activation during sensory integration was also found to be significantly heritable. Furthermore, dysconnectivity within the cerebellum was found in patients with schizophrenia when integrating auditory and visual stimuli. These findings highlight the role of cerebellar dysfunction in the pathophysiology of schizophrenia symptoms and its potential role as an endophenotype of schizophrenia spectrum disorders.