A cam follower unit comprising a tappet, a roller adapted to cooperate with a cam, the roller being mounted rotatably on a pin which is mounted in holes provided on two lateral ears of the tappet, the pin being retained in the tappet, in the longitudinal direction of the pin, by elastic spring retainers mounted against the ends of the pin, inside the holes of the lateral ears. The elastic spring retainers comprise a central portion adapted to be in contact with ends of the pin, the central portion defining a plane perpendicular to the central axis of the pin, and a peripheral portion adapted to exert a radial elastic force against an internal wall of the circular holes. The peripheral portion extends outwardly from the central portion and away from the pin along directions inclined with respect to the plane defined by the central portion.