To provide a control system for an internal combustion engine, which is capable of attaining both the securing of excellent drivability and the reduction of impact occurring when a movable part abuts against a restriction part at the same time. The control system 1 includes a variable valve lift mechanism 50 that changes a valve lift Liftin, and includes a restriction part 67a for having a movable part 65 abut thereagainst for restricting the valve lift Liftin such that it does not exceed a predetermined limit lift Liftin_L, and a variable intake air amount mechanism 11 that changes the intake air amount. The control system calculates a control input ULiftin for control of the variable valve lift mechanism 50, with a predetermined control algorithm including a disturbance suppression parameter POLE_lf (step 54), such that the valve lift Liftin follows up the target valve lift Liftin_cmd. When a determination that the movable part 65 has abutted against the restriction part 67a is made, the control system sets the disturbance suppression parameter POLE_lf such that the degree of suppression of the disturbance thereby becomes smaller than before the determination (step 73).