An electronic throttle control system and method are provided. The system includes a throttle valve, a motor configured to drive the throttle valve, and a throttle position sensor configured to detect an angle of the throttle valve. The system further includes an engine rotating speed detector, and a controller. The controller is configured to drive the motor to control the angle of the throttle valve. The controller is configured to initially set a lower limit value of the angle to an angle which is greater than a full closure angle of the throttle valve by a predetermined amount. The controller is further configured to, when a rise in an engine rotating speed is detected, re-set the lower limit value to reduce it by a predetermined amount to control the engine rotating speed to within a predetermined value from the preset idle speed.