An electromagnetic energy harvesting system that involves the use of wind-induced vibrations of an inclined stay cable is proposed for powering a wireless sensor node installed on a cable, which is important for monitoring the integrity of a cable-stayed bridge. The proposed system is developed by introducing the rotational mechanism of a rigid bar having a moving mass pivoted on a hinged point with a power spring, so that it can be successfully operated on an inclined cable. The performance of the proposed energy harvesting system is validated using its prototype by performing a shaking table test and a field test on an in-service cable-stayed bridge. In addition, strategies for improving the performance of the proposed system are discussed in detail, and the applicability of the system is investigated on the basis of these performance improvement strategies.