Cohesin is a conserved multisubunit protein complex with diverse cellular roles, making key contributions to the coordination of chromosome segregation, the DNA damage response and chromatin regulation by epigenetic mechanisms. Much has been learned in recent years about the roles of cohesin in a physiological context, whereas its potential and emerging role in tumour initiation and/or progression has received relatively little attention. In this Opinion article we examine how cohesin deregulation could contribute to cancer development on the basis of its physiological roles.