Shear strength of interfaces in virgin aggregate and in recycled aggregate concrete has been investigated using initially uncracked pushoff specimens by varying the following parameters: replacement level of the recycled aggregates (0 %, 50 %, and 100 %), concrete grade (normal strength and high strength) and the clamping force on the shear plane. The experimentally observed crack patterns in the pushoff specimens were indicative of the development of truss action for resisting interface shear. A truss-based analysis recommended in the literature, in combination with a simplified failure envelope for concrete subjected to biaxial stresses, has been used for shear-strength prediction of both the concrete types. The proposed methodology has been calibrated, with the help of the experimental results, to obtain a nominal distribution of shear stresses across the slip plane and conservative and reasonably accurate shear-strength predictions were noted for the selected experimental results taken from the literature.