Electroconvulsive therapy (ECT) is remarkably effective in severe major depressive disorder (MDD). Growing evidence has accumulated for brain structural and functional changes in response to ECT, primarily within cortico-limbic regions that have been considered in current neurobiological models of MDD. Despite increasing evidence for important cerebellar contributions to affective, cognitive and attentional processes, investigations on cerebellar effects of ECT in depression are yet lacking. In this study, using cerebellum-optimized voxel-based analysis methods, we investigated cerebellar volume in 12 MDD patients who received right-sided unilateral ECT. 16 healthy controls (HC) were included. Structural MRI data was acquired before and after ECT and controls were scanned once. Baseline structural differences in MDD compared to HC were located within the “cognitive cerebellum” and remained unchanged with intervention. ECT led to gray matter volume increase of left cerebellar area VIIa crus I, a region ascribed to the “affective/limbic cerebellum”. The effects of ECT on cerebellar structure correlated with overall symptom relief. These findings provide preliminary evidence that structural change of the cerebellum in response to ECT may be related to the treatment's antidepressant effects.