Stepped beam is one of the types of non-prismatic beams which can be applied to support a split level floor. Although strengthening with carbon fiber reinforced polymer (CFRP) is widely used for strengthening and retrofitted reinforced concrete beams, strengthening of stepped beams is still a challenge issue. In this paper, experimental and numerical investigations are presented to study the behavior of stepped reinforced concrete beams strengthened with CFRP. Seven stepped reinforced concrete beams having the same dimensions and reinforcement are fabricated to be tested up to failure. One beam is considered as control beam without strengthening, while five beams were strengthened with externally bonded CFRP sheets and the last one was repaired beam by CFRP. Analytical study is performed using ANSYS program to investigate 15 stepped reinforced concrete beams. 12 beams without strengthening with CFRP with different dimensions and 3 beams strengthened with CFRP. The ultimate load capacity increases due to strengthening with CFRP and by decreasing the height of stepped portion the ultimate load increases. Test results showed that, at the same load level the mid span deflection of the strengthened tested beams are smaller than the control beam due to CFRP sheets.