The synthesis of azobenzene-substituted polythiophenes (poly[3-(2-(4-((4’-ethoxyphenyl)-azo)phenoxy)ethoxy)-4-methylthiophene] (P3A), poly[3-((6-(4-((4’-ethoxyphenyl)azo)phenoxy)hexyl)oxy)-4-methylthiophene] (P3B)) and poly[3-(((6-(4-((4-ethoxyphenyl)azo)phenoxy)ethyl)tri(ethoxy)oxy)-4-methylthiophene] (P3C) has led to the development of novel photochromic polymers where the isomerization elf the photoactive side chains not only modifies their own UV-visible absorption but also induces a modification of the optical features associated with the conjugated backbone. These results seem to indicate that any perturbation of the side-chain organization in poly(3-alkoxy-4-methylthiophenes) could lead to a modification of the conformation of the main chain and, consequently, to chromic effects both in solution and in the solid state.