High-performance concrete (HPC) has become increasing popular in structural engineering. Capitalizing the advanced construction technology of 3D concrete printing (3DCP) and merits of HPC, structures with various profiles could be designed and constructed easily. As the mechanical properties of 3D printed concrete may be worse than the corresponding concrete cast by the conventional technology, this study proposes to evolve flexible fiber-reinforced polymer (FRP) grid as reinforcement for 3D printed HPC plates. Twelve plates were tested to explore the effects of the loading direction and fabrication type on the flexural behavior of FRP grid reinforced HPC plates. The results showed that the performance of the 3D printed HPC plates can be considerably enhanced owning to the FRP grid reinforcement. Additionally, the μCT-scanned images show that the pores between deposition layers were elongated due to the movement of the nozzle during printing, and the pores were stretched in the printing direction. The flexible FRP reinforcement may allow 3D printing of FRP reinforced concrete elements in the future.