A novel ternary mixed matrix membrane (MMM) with different amounts of filler loading (2, 4 and 6 wt.%) was fabricated, in which the synthesized Graphene Oxide (GO) nanoparticles incorporated into a polyvinyl alcohol (PVA) modified poly (ether-block-amide) (Pebax (R) 1657). PVA as an affordable additive provides a suitable affinity to separate CO2. Moreover, the presence of GO within the Pebax matrix causes an extra intermolecular space which enhances the CO2 permeability through the MMMs. In this study, pure Pebax membrane was modified via adding different amounts of PVA (0-20 wt. %). The results showed that the CO2 permeability increased from 79.42 barrer (for neat Pebax) to 81.24 barrer (for Pebax/PVA (10 wt.%)) and 90.7 barrer (for Pebax/PVA( 15 wt.%)) and also the CO2/CH4 selectivity increased from 12.37 (for neat Pebax) to 16.41 (for Pebax/PVA (10 wt%). Furthermore, the CO2/N-2 selectivity dramatically increased (from 36.93 for neat Pebax to 74.34 for Pebax/PVA(15 wt.%) at the pressure of 2 bar and temperature of 30 degrees C. The synthesized GO nanoparticles were incorporated (2, 4 and 6 wt. %) into the both Pebax/PVA( 10 wt.%) and Pebax/PVA(15 wt.%) matrix to fabricate the Pebax/PVA/GO MMMs. The results showed that the Pebax/PVA (10 wt.%)/GO (6 wt.%) with the CO2 permeability of 236.48 barrer and CO2/CH4 selectivity of 33.63 and also Pebax/PVA(15 wt.%)/G0 (6 wt.%) with CO2 permeability of 228.34 barrer and CO2/N-2 selectivity of 124.09 implied the best performance among all the prepared membranes for CO2/CH4 and CO2/N-2 separation, respectively. The Pebax/PVA/GO MMM indicates promising applications in CO2 separation processes. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.