A new method for creating layer-by-layer (LbL) assembled films on any substrate using polymers inspired by the high catechol content of mussel adhesive proteins is presented. Catechol-derivatized polymers permit LbL assembly on challenging substrates without prior surface preparation. Catechol groups incorporated into the LbL film induce the reduction of silver ions to metallic silver when immersed in an aqueous metal salt solution, providing antibacterial properties.