Prostate cancer is one of the most severe malignancies in men, and many genes and non-coding RNAs, included microRNAs (miRs), have been demonstrated to regulate prostate cancer progression. In the present study, we investigated the role of miR-671 in prostate cancer cell proliferation. We found that miR-671 was significantly upregulated in human prostate cancer tissues and cells. miR-671 overexpression promoted prostate cancer cell proliferation, while its downregulation inhibited prostate cancer cell proliferation, as determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays, colony formation assays, soft agar growth assays, and bromodeoxyuridine (BrdU) incorporation assays. miR-671 directly targets the 3′ untranslated region (UTR) of the tumor suppressor SOX6 (encoding SRY (sex determining region Y)-box 6) to inhibit its expression. Double knockdown of miR-671 and SOX6 promoted PC3 cell proliferation, suggesting that miR-671 promotes prostate cancer cell proliferation by inhibiting SOX6.