This paper presents a fractional-order adaptive mechanism based- Model Reference Adaptive System (MRAS) configuration for speed estimation of sensorless direct torque control of a five-phase induction motor. In effect, the fractional-order proportional-integral controller (FOPI) parameters are obtained by the PSO algorithm to enhance the MRAS observer response. So, the developed algorithm in the speed loop con-trol of the direct torque control strategy to increase its robustness against disturbances. Moreover, a comparative study has been done of the proposed MRAS-PSO/FOPI speed estimator with the conventional MRAS-PI and the PSO-based MRAS-PI. Simulation results have carried out of the different controllers used in the adaptation mechanism of the MRAS estimator, to show the performance and the robustness of the proposed MRAS-PSO/FOPI algorithm in term.