A simplified decoupling method is compactly extended for general nxn multivariable processes by introducing coefficient matching to obtain a stable, proper, and causal simplified decoupler. This simplified decoupling technique allows transfer functions of decoupled apparent processes to be expressed as a set of n equivalent independent processes and then derived as a ratio of the original open-loop transfer function to the diagonal element of the dynamic relative gain array. The advanced design of proportional-integral/proportional-integral derivative (PI/PID) controllers is then directly employed to enhance the overall performance of the decoupling control system while avoiding difficulties arising from properties inherent to simplified decoupling. The structured singular value theory is considered to ensure robust stability of decoupling control systems under multiplicative output uncertainty. Some industrial processes are considered to demonstrate the simplicity and effectiveness of the proposed method.