This paper presents and analyzes the experimental and numerical results of a series of direct shear tests performed under monotonic loading on a dune sand presenting two forms of compactness, one loose and the other dense, in contact with a rigid stainless steel plate presenting two forms of roughness, one smooth and the other rough. Experimental direct shear tests were performed using a shear box similar to Casagrande shear box. Calculations were carried out using two elastoplastic behavior models implemented into a finite elements computer program. Experimental and numerical results made it possible to determine the shear strength parameter characteristics of the sand–steel interface, and show a good agreement between the experimental and predicted data. In addition, for all considered normal stress levels, the rough interface is more advantageous than the smooth interface, and more true with dense sand than with loose sand of same type.