Composite electroactive materials of polyaniline and manganese oxide (MnOx) are obtained via layer-by-layer potentiodynamic deposition of MnOx from MnSO4 aqueous solutions on a stainless-steel electrode and subsequent electrosynthesis of polyaniline from aniline sulfate in 1 M H2SO4 on the MnOx surface. The composite electroactive materials demonstrated the characteristic redox properties of polyaniline in acidic aqueous solution. Characterization of the composite electroactive materials by the XPS method showed the amorphous nature of MnOx in the films in which manganese was in the +2, +3, and +4 oxidation states. The composite materials showed higher values of the specific capacitance (up to 2000 F/g on a weight of deposited-polyaniline basis) as compared with the pure polyaniline coating (228 F/g), measured at 1.0 A/g in 1 M H2SO4 solution. The composite electroactive materials obtained layerwise retained 90–100% of their capacitance after 2500 cycles and 500 charge–discharge cycles, with a Coulomb efficiency of 98%.