The effects of varying strain rates and deformation temperatures on the microstructure evolution of the FGH4113A alloy were investigated through hot compression experiments. During hot deformation, grain evolution is primarily governed by dynamic recrystallization (DRX) and twinning primarily. Furthermore, the pinning effect of the primary γ'''' phase (γ''''_p phase) plays a crucial role in grain refinement. Lower strain rates or higher temperatures facilitate DRX, twinning, and the dissolution of the γ''''_p phase. At 1140 °C, significant dissolution of the γ''''_p phase and the subsequent loss of its pinning effect reduce twinning activity. A unique twinning mechanism, termed “pinning twinning”, is identified, occurring exclusively under the influence of the pinning effect. When grain boundary migration fails to accommodate dislocations due to the pinning effect, grains preferentially eliminate dislocations via twinning, thereby reducing local strain energy. The grain size prediction model is improved by considering the pinning effect.