Background: Reduced cerebellar volumes and altered cerebellocerebral structural covariance have been reported in patients with schizophrenia. However, it is not clear whether such altered cerebellocerebral structural covariance would be observed before the onset of psychosis. We examined brain structural changes, including cerebral and cerebellar volumes, and cerebellocerebral structural covariance in individuals with attenuated psychosis syndrome (APS). Materials and methods: Twenty-one individuals with APS and 24 healthy controls (HC) were recruited and underwent structural MRI brain scan. Differences in voxel-based grey matter (GM) volume and cerebellar volume between the APS and HC groups were examined. The correlation between cerebellar volumes and voxel-based cerebral GM volumes were calculated to measure cerebellocerebral structural covariance in each group followed by group comparisons. Results: Compared with HC, individuals with APS exhibited extensive GM volume reduction in the frontal and striatal areas and reduced cerebellar volume. Structural covariance analysis indicated that the anterior and posterior parts of the cerebellum showed disparate correlation with cerebral voxel-based GM volumes. Abnormal cerebellar-cerebral correlation was also found in individuals with APS at the medial prefrontal gyrus. Conclusions: Our findings suggest that prefrontal and striatal structural changes as well as cerebellar structural covariance at the medial prefrontal gyrus may underpin the risk for psychosis and may serve as a potential target for early intervention in individuals at-risk for psychosis.