The three-dimensional (3D) printing technology has gained increasing attention in recent years. Even though the cementitious materials for 3D printing have been intensively investigated, little attention has been paid to the mechanical behaviors of 3D printed structural members. This paper was intended to investigate the mechanical behaviors of 3D printed fiber reinforced cementitious composite (FRCC) beams. Totally four 3D printed FRCC beams with different reinforcement methods, as well as one conventional steel reinforced FRCC beam, were fabricated and tested. The failure mechanisms were investigated and the effectiveness of different reinforcement methods was discussed. It was concluded that the 3D printed FRCC beams, with proper reinforcement method, could have comparable or even higher load-bearing capacity than conventional steel reinforced FRCC beam. However, the post-peak ductility of 3D printed FRCC beam is much lower due to the initiation of interlayer shear crack, indicating that the interlayer bonding strength of 3D printed FRCC should be further increased. The finite element (FE) model was also proposed to simulate the flexural behaviors of 3D printed FRCC beam as well as the conventional steel reinforced FRCC beam with identical steel reinforcements. The failure mechanism was analyzed and compared based on the proposed FE model. It was found that more steel reinforcements participated in bearing flexural load for 3D printed FRCC beam, thus the flexural bearing capacity of 3D printed FRCC beam is slightly higher than conventional cast-in-situ FRCC beam.