An experimental study on a series of composite beams combining a 250 mm (9.84 in.) deep reinforced concrete (RC) element and a 50 mm (1.97 in.) thick reinforced ultra-high-performance fiber-reinforced concrete (R-UHPFRC) element is presented. The specimens are tested in a cantilever-beam setup with the R-UHPFRC element acting as an additional tensile reinforcement. The test parameters include the span length and the ratio and type of the steel reinforcing bars, including stirrups. Most of the beams fail in flexure at a force that is 2.0 to 2.8 times higher than the resistance of the reference RC beams. The medium-span cantilevers with a low stirrup content failure along a flexure-shear crack. Near-interface concrete cracking softens the bond between the elements and enhances the member deformation capacity. The R-UHPFRC element contributes significantly to the shear resistance.