This paper presents a performance evaluation of a shaft speed control using a magnetorheological brake (MR brake). The MR brake consists of a rotating disk that is immersed in magnetorheological fluid (MR fluid). The rheology of the fluid changes under the influence of a magnetic field. Two controllers are proposed in this work: onoff and proportional-integral-derivative (PID). The on-off controller acts as the benchmark controller through computer simulation and experimental testing. Load tests have been considered in order to evaluate the controller's effectiveness in braking the wheel shaft at 50, 100 and 150 N in varying speeds of 300, 500, 700 and 900 rpm. The results obtained in the simulation and the experiment are compared and discussed. The PID controller shows good performance compared to the on-off control where the error percentages of the PID control, which are below 10%, are lower than the on-off controller.