In this study, a facile and novel facilitated transport mixed matrix membrane (FT-MMM) was fabricated by incorporating molecular amine functionalized polydopamine (PDA) into Pebax MH 1657. Polydopamine submicroparticles were chemically modified by tetraethylenepentamine (TEPA). The catechol groups on PDA can react with amino groups through the Michael addition reaction and Schiff base reaction. Grafting molecular amines onto PDA submicroparticles can not only improve interfacial compatibility between the fillers and a polymeric matrix but also enhance the facilitated transport of CO2 in the membrane because of the abundant CO2-philic groups. The effects of modified PDA submicroparticle content on the membrane permselectivity were investigated, and it was found that FT-MMM with a loading of 5% PDA submicroparticles exhibited the optimum CO2/CH4 separation property under humid conditions. The selectivity of Pebax-PDA/TEPA(5) membrane was 27.5, about 1.5-fold higher than that of the pristine Pebax membrane under identical operating conditions, while the membrane permeability remained comparable. Furthermore, the effects of operating pressure and temperature on the membrane separation performance were evaluated as well.