Polyethylene glycol (PEG) is an attractive additive for CO2-selective polymeric blend membranes due to the favorable dipole-quadrupole interaction between ethylene oxide units and CO2. In this study, we demonstrate a highly CO2 permeable membrane by blending poly(ether block amide) (Pebax) with in-situ self-assembled micellar structured poly(poly(ethylene glycol) methyl ether acrylate) (PPEGMEA). A series of Pebax/PPEGMEA membranes with either different PPEGMEA molecular weights or different PPEGMEA concentrations were prepared. Interestingly, the Pebax/PPEGMEA (30/70 w/w) blend membrane showed CO2-philic PPEGMEA micelles, which significantly enlarged the fractional free volume of the Pebax matrix. As a result, it exhibited unprecedented improvement in CO2 permeability by 1054% compared to the Pebax membrane while maintaining CO2/light gas selectivity.