TiAl alloys exhibit high specific strength and stiffness and especially excellent mechanical properties at elevated temperatures, making them appealing for high-temperature applications. Understanding the underlying creep mechanisms of TiAl alloys is essential for their design, fabrication and high-temperature applications. Here, we performed a series of large-scale atomistic simulations for high-temperature creep in nanocrystalline and nanotwinned γ -TiAl alloys. Our simulation results showed the influences of applied stress, grain size and temperature on the creep behaviors and mechanisms of nanocrystalline and nanotwinned TiAl alloys, which are in good agreement with predictions based on the classic Bird–Dorn–Mukherjee equation. (nhnhanh)