Additive Manufacturing (AM) is recently getting tremendous attention in many scientific fields. In this research, a civil engineering application of AM is investigated, where thirty small-scale cement mortar prisms reinforced with 3D-printed thermoplastics were tested in flexure. Rebar-like reinforcement were printed using a fused deposition modeling (FDM) printer. Five different thermoplastics were used with three different surface morphologies, obtained by introducing lugs on the rebar surface. The lugs were intended to enhance the reinforcement-matrix bond. Beams were tested in a three-point bending configuration to assess their load–deflection response and flexural ductility. In general, the introduction of lugs increased the load-carrying capacity of the specimen, between 40 and 120%. The ductility of beams was calculated based on displacement and energy methods.