This paper presents a three-dimensional nonlinear finite element (FE) model for prestressed concrete girders strengthened in shear with externally bonded carbon fibre reinforced polymer (CFRP) reinforcement. A total strain rotating crack model, where the crack direction changes with the change in the direction of the principal tensile stress, was used for the concrete. In this model, explicit modelling of the concrete shear behaviour after cracking, e.g. via a shear retention parameter, is not required as the crack plane is always a principal plane with no shear stresses. The FE model was validated using experimental results from the literature. An extensive parametric study was carried out to identify the effect of the concrete compressive strength, CFRP width-to-spacing ratio, CFRP thickness, girder effective depth, shear span to effective depth ratio, level of prestress, tendon profile, pre-cracking and CFRP-to-concrete interface model on the predicted shear force capacity. The results suggested that the predicted shear strength enhancement can be significant and increases with the increase in concrete compressive strength, CFRP width-to-spacing ratio, and CFRP thickness but decreases with the increase in girder effective depth and shear span to effective depth ratio.