The post-functionalization of poly(3-hexylthiophene) (P3HT) via various synthetic routes is reported. Well-defined and monofunctionalized ?-thiol-terminated P3HT, ?-carboxylic acid-terminated P3HT, ?-acrylate-terminated P3HT, and ?-methacrylate-terminated P3HT are obtained in high yields through a straightforward procedure. From those, different novel P3HT-based graft copolymers are synthesized following two routes: grafting onto and grafting through (macromonomer polymerization) methods. The synthesis of three types of graft copolymers is described. Each one has rod P3HT-grafted side chains on a coil main chain, which can be polyisoprene, poly(vinyl alcohol), or poly(butyl acrylate). Each copolymer is characterized by size-exclusion chromatography and NMR.