The strength of concrete elements can be greatly affected by elevated temperature as in fires, and so a great concern must be taken regarding its behavior under such condition. In this paper, a finite element model was built up using ABAQUS software to investigate the flexural behavior of reinforced concrete (RC) beams subjected to service load under elevated temperature. The beam was simply supported and was loaded at one-third and two-third of span length. The study consisted of three RC beams models; the first model simulated a control beam specimen at ambient temperature 20℃, while the other two models demonstrated damaged beams specimens according to two high temperatures 400℃ and 800℃, respectively. Each RC beam had 2 m span length, 300 mm height and 200 mm width. The steel reinforcement configuration was 3∅16 mm (Grade 60) main bars at the positive moment region in the beam bottom, 2∅14 mm (Grade 60) secondary bars at the beam top, and ∅10 mm /150 mm closed stirrups. The model was validated by comparing its results with the theoretical results from ACI code and literature. Several mechanical properties were investigated including concrete compressive strength, modulus of elasticity, and reinforcing steel yielding strength. The test results showed a reduction in the flexural capacity of the RC beams, tested at 400℃ and 800℃, of 17.6% and 88.2%, respectively, with respect to the control beam. The maximum service load carried by the beam, at one-third and two-third of the span length, decreased by 17.1% and 88.1% for the 400℃ and 800℃ high temperature, respectively. The results also showed an increase in deflection when the temperature increased due to the loss in stiffness.