This work investigates the impact of mobility degradation on endurance fatigue of a ferroelectric field-effect-transistor (FeFET) with the TiN/Hf0.5Zr0.5O2/SiOx/Si (MFIS) gate structure. We use the split capacitance–voltage ( C– V) method to study the carrier mobility during the program/erase cycling. We find that significant mobility degradation occurs with increasing program/erase cycle and further deteriorates endurance characteristics. Our work provides mobility degradation as another endurance fatigue factor of FeFET besides charge trapping and trap generation, which is helpful for endurance improvement.