Abstract High surface densities of properly oriented antibodies are desired for enhancing the sensitivity of immunosensors. A systematic investigation of the densities and orientations of antibodies, immobilized without and with intermediate protein molecules (protein-A and streptavidin) on nano-textured silicon surfaces (RMS roughness<100nm) was performed and the results were compared to those obtained from non-textured surfaces. The primary antibody densities and orientations (through densities of secondary antibodies) were quantitatively measured for the different cases. Higher densities were obtained for all nano-textured surfaces compared to non-textured ones. It was observed that higher primary antibody densities were obtained when no intermediate proteins were used. The different nano-texturing conditions did not have a significant effect on the densities with no intermediate proteins and with protein-A, but had an effect with streptavidin. The densities of the properly oriented primary antibodies increased on most of the nano-textured surfaces used as compared to the non-textured samples. The effect of the texturing on the densities was observed for several of the surfaces studied. Design nano-texturing could be used to maximize as well as tune the densities of the properly oriented antibodies on the substrate surface.