Synthesis of nanocomposite membranes composed of polymer and inorganic nanoparticles is an efficient method to improve separation properties of polymeric membranes because they possess properties of both organic and inorganic membranes such as good permeation properties, mechanical strength, and thermal and chemical stability. In this study, three types of nano-sized inorganic fillers (TiO2, SiO2 and Al2O3) were embodied into the poly (ether-block-amide) (PEBAX-1074) matrix to synthesize nanocomposite membranes and CO2/CH4 permeation properties of the membranes were investigated. The neat membranes were dense and prepared via solution casting; the solution blending technique was employed for synthesis of the nanocomposite membranes. Morphology of the membranes, formation of voids, and distribution of the nanoparticles were observed using FESEM analysis. Thermal stability of the membranes was examined using thermal gravimetric analysis (TGA). Fourier transform infrared (FTIR) spectra of the prepared membranes were analyzed to identify variations of the chemical bonds. The results obtained from the gas permeation experiments with a constant volume setup showed that the membrane incorporating Al2O3 nanoparticles has more ability in passing CO2 molecules compared to the two other fabricated membranes. (C) 2016 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.