TiAl alloys are attractive for high-temperature structural applications, yet their creep resistance and microstructural stability at high temperatures remain critical challenges. In this study, Ti45Al8Nb-0.6C alloy was prepared by vacuum induction melting to investigate its creep behavior and underlying deformation mechanisms at 800 °C under 200 MPa. The alloy exhibits a relatively homogeneous microstructure composed of (γ+α2) lamellar colonies, B2 phase, and blocky γ phase, with a creep life of 137 h and a typical ductile-brittle mixed fracture mode. Post-creep microstructural characterization reveals pronounced B2 phase formation, deformation twinning, lamellar coarsening, and abundant stacking faults at lamellar interfaces. Extensive dynamic recrystallization occurs during creep, leading to the formation of fine recrystallized grains. The Ti3AlC phase plays a dual strengthening role by effectively impeding dislocation motion and developing characteristic defect structures, including high-density dislocations and ladder-like stacking faults during deformation. These synergistic microstructural evolutions contribute to the enhanced creep resistance of the alloy.