Cell migration, which involves acto-myosin dynamics, cell adhesion, membrane trafficking and signal transduction, is a prerequisite for cancer cell metastasis. Here, we report that an actin-dependent molecular motor, unconventional myosin Va, is involved in this process and implicated in cancer metastasis. The mRNA expression of myosin Va is increased in a number of highly metastatic cancer cell lines and metastatic colorectal cancer tissues. Suppressing the expression of myosin Va by lentivirus-based RNA interference in highly metastatic cancer cells impeded their migration and metastasis capabilities both in vitro and in vivo. In addition, the levels of myosin Va in cancer cell lines are positively correlated with the expression of Snail, a transcriptional repressor that triggers epithelial-mesenchymal transition. Repression or overexpression of Snail in cancer cells caused reduced or elevated levels of myosin Va, respectively. Furthermore, Snail can bind to an E-box of the myosin Va promoter and induce its activity, which indicates that Snail might act as a transcriptional activator. These data demonstrate an essential role of myosin Va in cancer cell migration and metastasis, and suggest a novel target for Snail in its regulation of cancer progression.