Abstract: Cancer metastasis is a process by which tumor cells spread almost uncontrollably from primary tumor to form secondary tumors at a distant organ in the body. Elucidating the mechanism by which this complex process is controlled at the molecular level will be tremendously helpful in developing new therapeutic approaches for treating metastatic cancer. Small ubiquitin-related modifier(SUMO),a member of ubiquitin-like proteins,modifies a large number of transcription factors and coregulators. It has been reported that a number of cancer metastasis associated proteins undergo SUMOylation, including reptin, HIF-1α, Ets family, NF-κB. This article overviews these findings and discusses biological importance of protein SUMOylation in cancer infiltration and metastasis.