Strengthening substandard steel beams using Carbon Fiber Reinforced Polymer (CFRP) may be limited by the premature failure caused by debonding in the adhesive layer commonly used to attach the CFRP to the steel beam. Prestressing the (CFRP) lami-nates is a technique that can improve the effectiveness of such strengthening method and improve both the strength and serviceability behavior of steel beams by increasing the overall member stiffness. Previous studies introduced analytical models to predict the stresses distribution over the contact area between the (CFRP) laminate and the steel beam. However, such studies did not consider the importance of using mechanical an-chorage which was found essential to maintain the prestressing force in the (CFRP) la-minate. In this study, an analytical model is presented to predict the shear and normal stresses affecting the adhesive layer of steel I-beams subjected to flexural two point loads and strengthened with prestressed CFRP laminate when mechanical anchorage system is used. The equations were employed to calculate the stress on beams tested in an experimental program carried out to evaluate the performance of the proposed strengthening system.