All strengthened beams strengthened showed an increase in the ultimate load capacity of about 31 to 133% compared with the reference beams. In this study, most of the strengthened beams had deboned under sudden failure except the NSM-GFRP beams. The NSM-CFRP strengthened beams carried higher loads in terms of ultimate capacity than the NSM-GFRP strengthened beams but they showed less ductile behavior. The NSM-GFRP strengthened beam showed a good ductile behavior with high deflection values at ultimate load which were almost similar or even higher those recorded in the reference beams. This gave an amble warning before failure and can be considered an important advantage of strengthening RC beams with NSM-GFRP system.