In this paper, a method of controlling a MR fluid brake by simultaneously altering both the input current to the electric coil, and the MR fluid thickness between the stationary and rotating part of a single-disk brake was presented. In the development of the nonlinear torque-model for the brake, nondimensional analysis was used to generalize the problem for any brake configuration with similar attributes, while providing design guidance for making the energized and non-energized brake components comparable in strength. In order to control the brake speed, two saturating proportional-integral (PI) controllers were used in parallel: one for adjusting the MR fluid thickness, and the other for adjusting the input current to the electric coil. It was shown in this paper that the controller always achieves a steady-state output with zero error; however, the combination of fluid thickness and current is non-unique and depends upon initial conditions and saturation events that occur during the transient response. In conclusion, the control method proposed in this paper is shown to extend the range of torque capacity for the brake without increasing the radial envelope for the brake itself.