First examples of post‐polymerization functionalization of poly(3,4‐ethylenedioxythiophene) (PEDOT) derivatives are reported using tetrathiafulvalene (TTF) as a redox sensitive probe. EDOT derivatives bearing ω‐iodo‐alkyl or ω‐iodo‐polyether chains attached at the ethylenedioxy bridge have been electropolymerized and the resulting polymers have been derivatized using a TTF bearing a thiolate anion liberated under mild conditions. Cyclic voltammetry confirms the rapidity and efficiency of the derivatization process. This facile post‐polymerization functionalization coupled with the unique properties of PEDOT should lead to interesting developments in the field of modified electrodes, which includes selective electrochemical sensors.