The electropolymerization of thionine in an aqueous solution has been carried out by using both cycling voltammetry and chronoamperometry experiments. Electropolymerization has been applied at various pHs by using different working electrodes. The characterization of poly(thionine) thin films is performed by using cyclic voltammetry, current–time transients, atomic force microscopy, scanning tunnelling microscopy, ATR-FTIR, and UV–vis absorption spectroscopy techniques. It is deduced from current–time transients and morphological data that poly(thionine) film forms with random adsorption process and exhibits an irregular polymeric film. Poly(thionine) film formation was compared with that of previously published results of phenothiazine derivatives of poly(azure A) and poly(methylene blue). It has been concluded that type of amine functional group of phenothiazine dyes is very effective on the formation of polymeric film structure. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39686.