The m.3243A>G mutation is the most commonly observed mitochondrial mutation in humans. It causes a wide range of phenotypes, ranging from normal healthy aging to a severely affected quality of life through neuroradiological changes and cognitive impairment. Here, we studied the cerebellar changes in these patients and showed significant local reductions in gray matter tissue volume and functional connectivity using 7T MRI. Interestingly, its white matter remains relatively intact. Taken together, the current results contributes to the still limited understanding of brain pathologies in m.3243A>G patients.