In this study, a series of reinforced concrete beams were carried out to determine the size effect of the beams strengthened with different types of fiber reinforced polymer sheets (FRP). Two types of FRP sheets were considered in this study; Carbon and Glass fiber reinforced polymer sheets (CFRP and GFRP). FRP sheets were bonded to the soffit of the beams using a two-part Epoxy. These two types of FRP sheets were used to allow a variety of fabric stiffnesses and strengths to be studied. Also, this study introduced a new type of anchor to improve the efficiency of the FRP-strengthened beams and to prevent the anchor delamination of the FRP sheets. The results show that the strengthening system increases the ultimate capacity of the FRP-strengthened beams. Also, this increase depends on many parameters such as the type of the FRP sheets and size of the tested beams. Moreover, the beam size has significantly effected on the ductility of testing beams which increases as the size of beams decreases.