This study concerns the development of wear resistant coatings of Ni-Al2O3 composite on steel substrates by electrodeposition. Each of the coating experiments was performed in an electrolytic bath, containing a nano-sized dispersion of Al2O3 particles in nickel sulfate and boric acid solution. Composition of the coating mixture was systematically varied with respect to the contents of the dispersed particles, while the amount of the dissolved nickel sulfate, and boric acid and the applied current were kept constant during the experimental measurements. The coated substrates were characterized for their morphology, Vickers hardness, and scratch resistance properties. It was observed that hardness and scratch resistance of the coated substrates increased with an increase in the Al2O3 content in the coating. It was noted that hardness of the composite coating decreased after heat treatment at 400oC in air atmosphere.