Carbon nanotubes (CNTs) were incorporated in polyethersulfone hollow fiber mixed matrix membranes (P HFMs) to improve the gas separation performance. The P-CNTs (PC) HFMs were successfully developed using an indigenous spinning pilot plant. PC HFMs showed the improved thermal stability and mechanical strength as compared to that measured for the pristine P HFMs. The pure gas permeability of CO2, CH4, O2, and N2 gases for the developed HFMs were measured at 3 bar feed pressure and room temperature in a lab-scale gas permeation setup. It was observed that the presence of CNTs in PC HFMs significantly improved the CO2 permeability by four-fold to that measured for the pristine P HFMs. Furthermore, the ideal gas selectivity for CO2/CH4, O2/N2, and CO2/N2 gas pairs was also remarkably enhanced by almost 7-times, 1.5-times and 8-times, respectively, to that measured for P HFMs. The gas separation performance was better than or comparable to that of the literature-reported carbon nanomaterials-based membranes. Remarkably, the separation performance crossed or was almost closer to the upper bound curves drawn by Robeson in 2008 for these gas pairs. The improved separation performance can be attributed to the positive effect of doping of CNTs in HFMs, which resulted in selective transport of gases. Thus, the results, obtained in this study, experimentally demonstrated that the developed PC HFMs are a potential membrane material for industrially relevant CO2/CH4, O2/N2, and CO2/N2 gas separations.