Abstract The paper presents and extensive investigation on the bond behaviour between GFRP (glass fibre reinforced polymer) rebars and concrete. Pull-out tests were performed on helically wrapped and sand coated GFRP rebars with a wide range of diameters. Nonlinear finite element simulations of the tests allowed determining the effective distribution of the bond stress in the development length and the debonding propagation. An analytical model was developed to have an accurate prediction of the stress distribution at the interface and results were assessed with the numerical ones. Finally, the outcomes were compared with the design equations for the development length of FRP bars suggested in some design codes to assess their reliability.