AbstractAn innovative method to prepare poly(3,4‐ethylenedioxythiophene) (PEDOT)/MnO2 composite electrodes without adding any binder, conductive agent, or catalyst is reported. The preparation process for the supercapacitor electrodes is facile and involves simple spin coating and in situ polymerization of vacuum‐deposited 2,5‐dibromo‐3,4‐ethylenedioxythiophene. A uniform and stable PEDOT/MnO2 composite thin film is obtained after the in situ synthesis of the PEDOT thin film on the surface of the MnO2 nanoparticles with strong adhesion. The PEDOT/MnO2 supercapacitor electrodes exhibit excellent performance with a high specific capacitance of 575.0 F g−1 at a current density of 8 A g−1. The symmetrical supercapacitor offers an energy density of 14.6 Wh kg−1 with a high power density of 1365 Wh kg−1. Moreover, the PEDOT/MnO2 supercapacitor electrodes can be prepared from flexible substrates, of which the specific capacitance still reaches 352.9 F g−1 at a current density of 5 A g−1. The preparation method should facilitate the use of the multicomponent composite in further energy‐storage applications as well as in many other related fields.