The influence of amino-grafted nano-silica particles on the CO2/light gases separation performance of Matrimid mixed matrix membrane was evaluated. The aminosilane grafting reaction was performed using (3-aminopropyl) terimethoxysilane (APTMOS) as a silane coupling agent. Prepared membranes were studied through various methods including FTIR, SEM and TGA. To evaluate the gas separation performance, pure CO2, CH4, N2 and O2 permeation tests were conducted using constant volume-varying pressure set-up with various upstream pressures. Characterization results demonstrated the appropriate dispersion of silica particles within the Matrimid matrix as well as a suitable interaction between polymer/filler phases. Results from the gas permeation study confirmed that the permeability of all gases except CO2, decreased as silica content increased in Matrimid matrix. Nevertheless, the CO2 permeability increased from 4.20 Barrer in neat Matrimid to about 9.59 Barrer at 20 wt% loading of silica. The selectivity of O2/N2, CO2/N2 and CO2/CH4 pair gases was enhanced by increasing the nano-silica content. The selectivity of CO2/N2 and CO2/CH4 was increased from 18.27 to 50.74, and 20.01 to 70.51, respectively.