A control system for a plant is provided. A feedback control input is calculated so that a controlled output of the plant coincides with a target value. The feedback control input is averaged to calculate an averaged feedback control input. A hold control input is calculated according to an operating condition of the plant. A corrected hold control input is calculated by combining the hold control input with the averaged feedback control input according to a preset ratio. A control input to the plant is set to the feedback control input in a first state where a control deviation between the controlled output and the target value is greater than a predetermined threshold value, and setting the control input to the corrected hold control input in a second state where the control deviation is equal to or less than the predetermined threshold value. The feedback control input is made to gradually approach to or coincide with the corrected hold control input in the second state.