A passenger protection system includes: first and second sensors that detect an impact applied to a vehicle in a width direction; a determination device that determines a collision by comparing a first detection signal from the first sensor with a first determination condition, and by comparing a second detection signal from the second sensor with a second determination condition; and a boarding position detector that detects a boarding position of a passenger. The determination device sets the first determination condition and the second determination condition according to the boarding position in such a manner that the first determination condition is different from the second determination condition.