This paper presents a study of a system of post-tensioned structural glass beams. In order to increase the initial fracture strength of glass beams and provide residual load-carrying capacity in the event of glass failure, annealed laminated glass beams are reinforced with flat stainless steel tendons, which are pre-tensioned and bonded to the lower edge of the beam. When the adhesive has cured, the pre-tension is released, inducing a compressive pre-stress and an upwards bending moment on the beam. The behaviour of these post-tensioned beams is compared to reinforced beams (without post-tensioning) and reference beams (without reinforcement) through series of four-point bending tests. The results show a highly improved performance of the beams, both before and after initial glass fracture.