miR-378 has been proven to inhibit cell growth, migration and invasion in different types of cancers. In this study, we found that miR-378 was commonly downregulated in the bone marrow cells obtained from myelodysplastic syndrome (MDS) patients. We further investigated the role of miR-378 in the proliferation and apoptosis of SKM-1 cells, an acute myeloid leukemia cell line established in the leukemic phase during the progression of MDS to AML (MDS/AML). Results indicated that overexpression of miR-378 in SKM-1 cells interfered with proliferation via inducing apoptosis and G0/G1-phase cell cycle arrest, and suppressive effect of miR-378 on MDS/AML cells may be mediated partly through Bcl-w and CDC40. Moreover, apoptosis induced by miR-378 correlated with increased expression of Bax and activation of caspase-3, -8 and -9. Taken together, our data support a critical role for miR-378 in the pathogenesis of MDS and provide a novel therapeutic target in this complex disease.