This study investigates the impact of carbon fiber reinforced polymers (CFRP) composite to concrete bond strength degradation on the flexural response of CFRP strengthened reinforced concrete (RC) beams by using nonlinear finite element analysis (NLFEA). After reasonable validation of NLFEA simulated beams with the experimental test results of companion beams, NLFEA was expanded to provide a parametric study of twenty-two beams that correlates the ultimate flexural strength of RC beams to degradation in concrete compressive strength, degradation in bond strength, CFRP bond surface with concrete, and the number of layers and the size effect. The results show that the increase of CFRP-to-concrete contact area, concrete strength degradation, and epoxy bond strength degradation percentage had a significant impact on ultimate load capacity, ultimate deflection, stiffness, and energy absorption. Finally, new guidelines were proposed for designers and researchers to find the reduction in concrete strength as well as CFRP-to-concrete contact area at any ultimate load capacity of RC beams.