Fesselin is an actin binding protein from smooth muscle that nucleates actin polymerization in a Ca++-calmodulin dependent manner, bundles actin and inhibits the actin-activated ATPase activity of myosin S1. We now report that fesselin binds to smooth muscle α-actinin. Binding was measured by blot overlay, affinity chromatography and sedimentation methods. Binding was moderate with an association constant of 1-4×107 M−1 assuming a 1:1 association of fesselin with α-actinin. Fesselin binds to the central spectrin domain repeat region of α-actinin but not to the CH1-CH2 domain. Fesselin accelerates the polymerization of actin. This activity of fesselin was attenuated by α-actinin. These observations support the role of fesselin in organizing the cytoskeleton.