Aberrant sialylation catalyzed by sialyltransferases (STs) is frequently found in cancer cells and is associated with increased cancer metastasis. However, ST inhibitors developed till now are not applicable for clinical use because of their poor cell permeability. In this study, a novel ST inhibitor AL10 derived from the lead compound lithocholic acid identified in our previous study is synthesized and the anti‐cancer effect of this compound is studied. AL10 is cell‐permeable and effectively attenuates total sialylation on cell surface. This inhibitor shows no cytotoxicity but inhibits adhesion, migration, actin polymerization and invasion of α‐2,3‐ST‐overexpressing A549 and CL1.5 human lung cells. Inhibition of adhesion and migration by AL10 is associated with reduced sialylation of various integrin molecules and attenuated activation of the integrin downstream signaling mediator focal adhesion kinase. More importantly, AL10 significantly suppresses experimental lung metastasis in vivo without affecting liver and kidney function of experimental animals as determined by serum biochemical assays. Taken together, AL10 is the first ST inhibitor, which exhibits potent anti‐metastatic activity in vivo and may be useful for clinical cancer treatment. J. Cell. Physiol. 223: 492–499, 2010. © 2010 Wiley‐Liss, Inc.