In this study, the capability of a mixed matrix composite membrane (MMCM) fabricated using polyether block amide polymer PEBAX MH1657 from Arkema and in lab synthesized aminated partially reduced graphene oxide (A-prGO) nanofiller as a selective layer has been studied for gas separation. Moreover, the effects of nanofiller addition on membrane structure properties and performance were examined. The PEBAX/A-prGO membrane was fabricated as a selective layer on top of a supporting substrate layer of polysulfone 1700. MMCM was prepared in five different loadings of A-prGO nanofiller (0, 0.05, 0.1, 0.2, 0.6 (w/w)%) of the used PEBAX amount. The synthesized nanofiller and fabricated MMCM were characterized using different characterization tests (XRD, FFIR, EDX, and SEM). The optimum separation of the membrane was found when the loading of A-prGO was 0.1%. The permeability of the membrane for CO2, N-2 and CH4 gases were 47.5 Barrer for CO2, 0.45 Barrer for N-2 & 2 Barrer for CH4 while the selectivity of CO2/N-2 and CO2/CH4 are 105.6 and 23.75, respectively. Surprisingly, the fabricated membrane performance found to be above the Robeson 2008 upper bound of permeability-selectivity relation for CO2/N-2 gases separation.