There is described an expanding blind rivet assembly having a flange (3) provided with an undercut surface facing the rivet shank. A resilient cap (20) is formed with a cavity (22) having an opening surrounded by an undercut surface (23) within the cavity, so that the cap may be snap-engaged over the flange of the rivet after setting. The cap provides abrasion and corrosion protection for the flange. The cap (20) may also be provided with securing means for securing a further component to the cap (20).