A pulley device comprising a pulley and a bearing. The pulley has at least one “C-shaped” pulley part having an inner portion mounted on the bearing, an outer portion having an outer cylindrical surface dedicated to interact with a belt or a chain, and an intermediate portion extending substantially radially between axial ends of inner and outer portions on one axial side of pulley device. The outer cylindrical surface of outer ring is provided with at least one recess having in cross-section, a concave internal profile. The pulley part is provided with at least one protruding portion which inwardly extends beyond the inner cylindrical surface of inner portion. The protruding portion is received in a corresponding recess of outer ring so as to block the pulley part with respect to the outer ring in both axial directions.