The purpose of this study was to evaluate the reinforcing effect of fiberglass on composite resin retainers of the telescopic dentures. A finite element method was used to assess the effect of the abutment height and the embedment of the fiberglass on the stress distributions of the retainers. The experimental retainers of Poly(methylmethacrylate), composite resin (CR) and the fiber-reinforced composite resin (FRC) were used in the fracture test. The fracture load of the FRC retainers were significantly greater than those of the other retainers. The embedment of the fiberglass reduced the stress at the upper surface of the CR retainers. The fracture origin in the CR retainers was seen on the upper surface, while that of the FRC was at the cervical region near the abutment. These results suggest that the change in the fracture pass by the fiberglass increased the fracture resistance of the CR retainer.