The formation of the composite of reduced graphene oxide (RGO) with poly-o-phenylenediamine (PPD) on the surface of SnO2-coated conducting glasses (CG) is studied by the methods of voltammetry, atomic force microscopy (AFM), electron microscopy (SEM) with energy-dispersive X-ray spectroscopic (EDXS) microanalysis, and electron spectroscopy, When a CG with deposited graphene oxide is placed into aqueous solution of o-phenylenediamine (OPD), the monomer is strongly fixed in the GO matrix, as confirmed by EDXS data. The further redox interaction in the two-phase system GO–OPD initiates polymerization of OPD in the GO film. When anodic polarization in switched on, the oxidation and the further polymerization of OPD go on, while GO is reduced to RGO as a result of mediated reaction to yield the RGO–PPD composite even in the absence of cathodic polarization. The electron spectra of composites reveal the presence of an absorption band close to absorption of individual PPD. According to AFM and SEM data, OPD incorporated into the composite structure keeps RGO from being folded in acidic media. As the time of impregnation increases, the degree of reduction of GO to RGO changes, which is reflected in the surface morphology and the amount of monomer in the composite (RGO–PPD)-1. The coating becomes black, which is typical of RGO, and its conductivity increases by 4–5 orders of magnitude. [ABSTRACT FROM AUTHOR]