Genistein, an isoflavone isolated from soybean, has been found to be a potent antitumor agent. However, both the effect of genistein on human uveal melanoma cells and the precise mechanism by which genistein suppresses tumorigenesis remain unclear. In the present study, we explored the possible activity of genistein to inhibit human uveal melanoma cell growth and investigated the possible role of genistein on microRNA-27a (miR-27a) as well as its target gene zinc finger and BTB domain containing 10 (ZBTB10) expression levels. The results suggested a significant inhibition of uveal melanoma cell growth in a time- and dose-related manner. In vivo study also indicated treatment groups with genistein could significantly inhibit the growth of xenografts. Further functional assays revealed that the levels of miR-27a and its target gene ZBTB10 were significantly different based on the dose of genistein. In conclusion, the present study demonstrates that genistein exerts growth inhibitory activities in human uveal melanoma cells. Moreover, we for the first time report a correlation between antitumor activity of genistein and miR-27a mediated regulatory mechanism.