An experimental program was performed through this research to assess the flexural strengthening capacity of reinforced concrete beams strengthened using Near Surface Mounted CFRP laminates under various sustained loads in order to examine the effects of strengthening RC beams under sustained loads. Six tests were performed on five R.C. beams under four point bending. The specimens included one control beam without strengthening and four beams strengthened with two, 2 cm wide strips of CFRP laminate. One specimen was not subjected to sustained load for comparison while all the other beams were strengthened under a sustained load. Two beams were strengthened under a sustained load of 65% of the failure load one of which was wrapped with 50cm wide FRP sheets at the end points of the strips. The third specimen was strengthened under a sustained load of 90 % of the failure load of the control beam. In the last test the control beam was strengthened and reloaded to failure. Test results showed that beams strengthened under sustained load at the two levels, showed only a 11.2 % decrease in the enhancement ration compared to the beam strengthened without sustained load, while reloaded beam showed a 17.8% % decrease. The beam strengthened mechanically in the transverse direction with FRP sheets in addition to the laminates showed an increase in the enhancement ratio capacity by 13.1%% compared to the beam strengthened without sustained load.