Galectins are a taxonomically widespread family of glycan-binding proteins, defined by at least one conserved carbohydrate-recognition domain with a canonical amino acid sequence and affinity for β-galactosides. Because of their anti-adhesive as well as pro-adhesive extracellular functions, galectins appear to be a novel class of adhesion-modulating proteins collectively known as matricellular proteins (which include thrombospondin, SPARC, tenascin, hevin, and disintegrins). Accordingly, galectins can display de-adhesive effects when presented as soluble proteins to cells in a strong adhesive state. In this context, the de-adhesive properties of galectins should be considered as physiologically relevant as the proadhesive effects of these glycan-binding proteins. This article focuses on the roles of mammalian galectins in cell adhesion, spreading, and migration, and the crossregulation of these functions. Although careful attention should be paid when examining individual galectin functions due to overlapping distributions, these intriguing glycan-binding proteins offer promising possibilities for the treatment and intervention of a wide variety of pathological processes, including cancer, inflammation, and autoimmunity.