MicroRNAs (miRNAs) have emerged as post-transcriptional regulators that are critically involved in the pathogenesis of a number of human cancers. Recently, cyclin-dependent kinase 6 (CDK6) is found to be up-regulated in several types of human tumors and has been implicated in cancer initiation and progression. We have identified miR-107 as a potential regulator of CDK6 expression. A bioinformatics search revealed a putative target site for miR-107 within the CDK6 3' untranslated region. Expression of miR-107 in gastric cancer cell lines was found inversely correlated with CDK6 expression. miR-107 could significantly suppress CDK6 3' UTR luciferase reporter activity, and this effect was not detectable when the putative 3' UTR target site was mutated. Consistent with the results of the reporter assay, ectopic expression of miR-107 reduced both mRNA and protein expression levels of CDK6, inhibited proliferation, induced G1 cell cycle arrest, and blocked invasion of the gastric cancer cells. Our results suggest that miR-107 may have a tumor suppressor function by directly targeting CDK6 to inhibit the proliferation and invasion activities of gastric cancer cells.