Commercial poly (ether-block-amide) (Pebax®) copolymers are thermoplastic elastomers that have attracted attention as membrane materials due to their high performance in CO2 separation. In this study, a cross-linking reaction is reported as a viable strategy to improve the gas separation performance of a highly permeable but low selective Pebax 2533 membrane. To this end, a new bi-functional aminosilane cross-linker (3-aminopropyl(diethoxy)methylsilane (APDEMS)) was applied. Cross-linked Pebax 2533 membranes were prepared via solution-casting with different amounts of APDEMS ranging from 0.5 to 4 wt%, to investigate the effect of the aminosilane concentration on the membrane performance. Gas separation with prepared membranes was studied for CO2/N2 at the feed pressure ranges of 2-10 bar. Instrumental analyses were applied to investigate the effect of the cross-linking reaction on the structure and properties of the membranes. The results showed that a 2 wt% APDEMS cross-linked Pebax 2533 membrane has the best gas separation performance. The CO2/N2 ideal selectivity of the cross-linked Pebax 2533 increased twice compared to the neat Pebax 2533 membrane at the feed pressure of 2 bar, while the CO2 permeability experienced a slight decrease by cross-linking, but still remains higher than the permeability of other Pebax grades.