TiN and Ti–Al–Si–N nanocomposite coatings of the type nc-TiAlN/a-Si3N4 have been prepared by cathodic arc physical vapour deposition process using cylindrical cathodes on high speed steel substrates with different surface roughness values, where the roughness is induced by emery paper method and diamond hand polishing. Fracture toughness studies by indentation method have shown that TiN is tougher than Ti–Al–Si–N nanocomposite coatings. Scratch and pin on disc wear tests have been conducted on the specimens to study the adhesion and tribological behaviour of these coatings respectiely. The wear mode between two mating surfaces is complex, and the wear behaviour can be understood better by studying the progression of surface changes and wear debris. The adhesion pattern of harder nanocomposite coating on smooth substrate surfaces is different from that of tougher TiN coating. Wear volume of these coatings decreases with substrate roughness, but it is found more for nanocomposite than for TiN.