Functions of the cell cortex, including motility, adhesion, and cytokinesis, are mediated by the reorganization of the actin cytoskeleton. The assembly of the cytoskeletal components at cortical sites is regulated dynamically in a temporal and spatial manner. Recent evidence indicates that the formin family proteins play a crucial role in the reorganization of the cytoskeleton. In this review, recent advance in the understanding of the functions of formin family proteins is discussed.