Spinocerebellar ataxia (SCA) is a devastating progressive neurodegenerative disorder, for which no effective treatments have been developed. However, some studies have shown that an intracerebellar or intrathecal injection of mesenchymal stem cells (MSCs) was partially effective in some genetic mouse models of cerebellar ataxia such as SCA1 and Lurcher mutant. MSCs likely exert their therapeutic efficacy by secreting innate factors to induce neuronal growth and synaptic connection and reduce apoptosis. In this review, we introduce the therapeutic influence of MSCs on each mouse model for cerebellar ataxia and the possible mechanisms underlying the action of MSCs. We also introduce studies on the safety and effectiveness of umbilical cord MSCs for patients with SCA.