A facilitated transport polyamide (PA) membrane was developed for gas separation by interfacial polymerization reaction of piperazine (PIP) and isophthaloyl chloride (IPC) supported on polysulfone (PSF) membrane previously prepared by dry/wet phase inversion method. The properties of the prepared membranes were characterized by SEM, FT-IR, TGA, and XRD. SEM images showed that a defect-free PSF, and rough PA membranes were fabricated, while the FT-IR spectra confirmed the formation of PA layer on top of the PSF support. The separation performance of the thin film PA and PSF membranes was evaluated using four gasses (CO2, CH4, N2, and O2). Compared to the PSF membrane, the PA membrane demonstrated an increased selectivity of CO2/CH4 and CO2/N2 by 178%, 169%, respectively. This improvement was attributed to the presence of amine functional groups, which acted as a fixed carrier to facilitate the transport of CO2 gas across the membrane. However, building the PA layer on top of PSF support reduced the membrane permeance of CO2 from 2.41 to 2.12 GPU as a result of the increased mass transfer resistance. Furthermore, the effect of operating temperature and pressure on the separation performance of the membranes was investigated.