A method of synthesis leading to poly(3-alkylthiophene)s with two different functional groups in the side chain, one of which is an NLO-active chromophore, has been developed. This method, based on the post-functionalization of a reactive homopolymeric precursor, permits to prepare different polyfunctional polymers that are fully soluble in the most commonly used organic solvents. The procedure is very easy to perform, cost-effective, highly versatile and reproducible.