In this study, we investigated the roles of miR-132 in tumor growth of osteosarcoma. We found that overexpression of miR-132 significantly suppressed in vitro cell proliferation and in vivo tumor growth. In addition, miR-132 overexpression induced G1/S cell cycle arrest of osteosarcoma cells. Further study showed that miR-132 could interact with the 3′-untranslated region of cyclin E1 (CCNE1) gene and repress its expression. Re-expression of CCNE1 (without the 3′UTR) could partially abrogate the miR-132-induced cell proliferation inhibition. Of significance, contrary to CCNE1, expression level of miR-132 was significantly lower in osteosarcoma tissues than in the adjacent normal tissues. Taken together, these results indicate that miR-132 functions as a tumor suppressor in osteosarcoma and that its suppressive effects are mediated chiefly by repressing CCNE1 expression.