Abstract: A roller cam follower, especially an engine hydraulic roller lifter, is restrained from rotation away from a position in which the roller rotates squarely on its associated cam by a retainer clip fixed on the lifter body and having a tang with flat sides engaging an axial groove in an associated bore of the engine lifter gallery. The retainer clip is a closed ring with opposite flexible hat sections connected by arches having inner edges that snap into a groove on the lifter body. The inner edges are preferably angled upward to aid installation and the hat sections preferably have squared inner ends that engage flats on the lifter body to prevent relative rotation of the body and clip.