An important problem for the vacuum gas oil (VGO) hydrocracking process is to control the product yield, which is difficult to measure online. In the present study, the performance of a single input single output (SISO) control loop provided for a pilot scale VGO hydrocracker is studied. The controller aims to set the yield of the process at the desired value by manipulating the reactor temperature. To do such a task, the dynamic model of the reactor is solved by the using conservation element/solution element (CE/SE) method; then, a PID (proportional-integral-derivative) controller, tuned using the genetic algorithm method, is applied to control the yield of the process. Results show that the reference yield of the process is accurately tracked that guarantees the production of the naphtha and middle distillate at the desired values. In addition, no temperature overshoot is observed, thereby protecting the catalyst from premature deactivation.