Abstract—This study focuses on the design of the decentralized Proportional-Integral-Derivative (PID) controller for a coupled flotation system. It emphasizes the difficulties encountered when dealing with interconnected Multiple-Input Multiple-Output (MIMO) systems that cannot be effectively regulated using traditional linear feedback controllers. The significance of this article lies in its examination of how the Relative Gain Array (RGA) can be utilized to mitigate the impact of process connections. With the use of a thoughtful selection of single-loop pairings, the decentralized controller is created following the RGA technique. The decentralized controller that has been developed serves the purpose of reducing the influence caused by process interfaces. A set-point tracking technique, based on Internal Model Controllers (IMCs) is adopted in the design. The system time response and overshoot were also analyzed. The paper proposed a decentralized control mechanism and provided a comprehensive process for applying it to both the system under investigation and different MIMO industrial processes. The performance of the suggested closed-loop system was simulated and confirmed using Matlab/Simulink.