The present study concerned with studying the flexural behavior of RC beams with stay in place (SIP) forms, which can be used as a novel construction technology. Eight specimens were prepared, five of them with SIP form and three specimens were prepared conventionally. The specimens were tested in flexure under four-point bending loads. All the specimens had hollow unreinforced longitudinal PVC tube, located at tension side to reduce specimen weight. The used SIP forms were made from glass fiber reinforced polymer (GFRP). The GFRP forms were extended at compressive side forming hooks in order to enhance their bond with concrete and, also, to avoid a premature lateral local buckling. The forms were provided, also, with lateral clips GFRP to improve their bond with concrete, and to avoid a premature lateral buckling. The tested specimens can be divided into three groups. The first group contains three specimens, which prepared conventionally (without SIP forms) with different reinforcement steel bars (10, 12 or 16 mm diameter) at tension side. The second group includes three specimens similar to those of the first group but with SIP forms. The third group contains two specimens similar to the first specimen of the second group but they were strengthened at tension side with additional longitudinal sheets of carbon fiber reinforced polymer (CFRP) or glass fiber reinforced polymer (GFRP) in order to increase their flexural resistance. The experimental results included ultimate load, load-deflection and load-strain relationships. The cracking behavior and failure mode were observed and recorded. The experimental results showed a significant improvement in the flexural behavior of the tested specimens with SIP forms compared to the corresponding conventional ones. The tested specimens were simulated numerically using ANSYS (version 15). The numerical values of ultimate load were almost higher than the corresponding experimental value; up to 18%.