Membrane gas separation is a prospective technology for hydrogen separation from various refinery and petrochemical process streams. To improve efficiency of gas separation, a novel hybrid membrane consisting of nanodiamonds and P84 copolyimide is developed. The particularities of the hybrid membrane structure, physicochemical, and gas transport properties were studied by comparison with that of pure P84 membrane. The gas permeability of H ₂, CO ₂, and CH ₄ through the hybrid membrane is lower than through the unmodified membrane, whereas ideal selectivity in separation of H ₂/CO ₂, H ₂/CH ₄, and CO ₂/CH ₄ gas pairs is higher for the hybrid membrane. Correlation analysis of diffusion and solubility coefficients confirms the reliability of the gas permeability results. The position of P84/ND membrane is among the most selective membranes on the Robeson diagram for H ₂/CH ₄ gas pair.