A safeguard system for a vehicle is provided which works as an unintended operation control system. The safeguard system works to calculate an accelerator-manipulated variable representing a degree to which an accelerator of the vehicle is manipulated. When it is found that the accelerator-manipulated variable has dropped at a given rate and then risen within a preselected rise time period, the safeguard system determines that such an operation is an unintended action and controls an operation of the vehicle such as acceleration or speed of the vehicle to minimize the probability of encountering a hazard to the vehicle.