The present disclosure provides a system and method for determining whether to start an engine. The system includes an engine configured to provide driving force for a vehicle through combustion of fuel, a motor configured to provide driving force for the vehicle using electrical energy, an engine clutch connecting the engine and a drive shaft, and a controller configured to control engagement of the engine clutch and starting of the engine. The controller calculates a predicted vehicle speed at the time of engagement of the engine clutch based on the current vehicle speed upon a request for passive run driving of the vehicle. The controller determines whether to start the engine by comparing the predicted vehicle speed with a reference vehicle speed.