The tension capacity of fiber reinforced polymer (FRP) bars or strips mounted in grooves realized on the surface of existing concrete, masonry or timber structural elements, usually indicated as near surface mounted (NSM) technique, has been examined in the recent years by means of several experimental tests, supported by a large amount of numerical and theoretical studies too. In this paper, since the performance of the strengthened elements is based on the bond behaviour at the concrete-reinforcement interface, the analysis of bond behaviour of FRP-NSM systems is carried out considering a simplified rigid-softening relationship followed by a frictional constant strength branch. Based on this assumption, an analytical formulation for predicting the end-debonding stress in FRP-NSM applied over concrete elements is derived. The reliability of the proposed mechanical model has been checked on the basis of the comparisons with numerous experimental data of bond tests available in the international literature and collected by the authors. A design formula for calculating the debonding load in FRP-NSM systems has also been calibrated in agreement with the provisions of Annex D included in EN 1990 (Design assisted by testing).