Cerebellar injury has been increasingly recognized as a complication of preterm birth, with decreased cerebellar volumes seen on follow-up neuroimaging. A cohort of 38 preterm newborns, including 14 with two scans, was studied with MRI, including single-shot fast spin-echo diffusion tensor imaging (DTI) sequence specifically to assess the posterior fossa. Early changes in the cerebellum [apparent diffusion coefficient (ADC) and fractional anisotropy (FA)] were assessed and correlated with supratentorial manifestations of injury [intraventricular hemorrhage (IVH) or white matter injury (WMI)]. ADC decreased and FA increased with increasing gestational age in both cerebellar gray and white matter. Severe IVH was associated with increased ADC in the middle cerebellar peduncles and hila of the cerebellar nuclei, decreased ADC in the cerebellar cortex, and decreased FA in all three regions. Changes with WMI were not consistent. Significant developmental changes in water diffusion were seen in cerebellar gray and white matter that were altered in patients with supratentorial IVH. DTI studies may provide an early indicator for cerebellar injury and abnormal cerebellar development in preterm neonates.