A twin rotor multi-input multi-output system (TRMS) is a nonlinear system with cross couplings between two inputs and two outputs. TRMS has been studied heavily in research as a benchmark for evaluation of control algorithms. In this paper, a state feedback decoupler is developed for the TRMS and investigated against a simplified decoupling approach. Then, a fractional order PID (FOPID) controller is designed for the decoupled TRMS. FOPID controller parameters were determined by applying Simulated annealing (SA) heuristic optimization algorithm in order to find the optimal controller parameters. The main goal of a decoupler is to guarantee time response specifications and eliminate cross-coupling interactions. The state feedback decoupler and their controllers are applied in the process simulation, and the outputs are examined. The overall control structure of the FOPID with the state feedback decoupler is evaluated and assessed for various reference commands to exhibit the applicability of the developed approach.