A tendency towards an increase in the microhardness of a chromium coating from adding carbon nanomaterials (nanodiamonds, single-wall and multiwall nanotubes, and graphene oxide) to a standard chromium plating electrolyte, both separately and in the form of a mixture. Based on the analysis of the Raman spectra of the nanocarbon modifiers used and the mechanical characteristics of the modified composite chromium coatings, it is shown that a correlation between the defectiveness level of the carbon nanomaterial added to the galvanic electrolyte and the microhardness of chromium coatings exists, which has made it possible to confirm the hypothesis put forward.