Micrometer and nanometer Al particles were codeposited with nickel by electrodeposition from a nickel sulfate bath containng a similar content of Al particles. The effect of Al particles size on the microstructure of the electrodeposited Ni-Al composite coatings was analyzed. The results indicated that at a given Al particles content the incorporation of Al nanoparticles instead of the microscale countparts significantly increased the particle number per unit volume in the composite, led to a more homogeneous distribution of particles, and finer Ni grains due to nucleation of smaller Ni grains on the surface of Al nanoparticles, which changed the direction of the local Ni growth and caused the formation of a fine equiaxed grain structure. (C) 2009 Elsevier B.V. All rights reserved.