Poly(4‐anilino‐1‐butanesulfonic acid) sodium salt was synthesized from the electrochemical oxidation of 4‐anilino‐1‐butanesulfonic acid sodium salt, which was readily obtained from aniline and 1,4‐butane sultone. The resulting water‐soluble polymer has shown much higher redox cyclability than unsubstituted polyaniline, which was demonstrated by an in situ spectroelectrochemical and a cyclic voltammetric study.