Abstract The microstructures and tensile properties of Ni coated nano-sized TiN particle reinforced Al–Cu matrix composites via casting were studied. It was found that with the increase of the TiN particle addition, the average size of the α-Al grains decreases. The nano-sized TiN particles enclosed inside the α-Al grains provide some heterogeneous nucleation sites during solidification, resulting in a more refined microstructure. Moreover, the θ' precipitates in the composites matrix were much finer and more uniformly distributed. After T6 heat treatment, the strength and ductility of the composites increase simultaneously. The yield strength, ultimate strength and elongation of the 2.0wt% nano-sized TiNp/Al–Cu composite can reach to 365MPa, 594MPa and 13.5%, increased by 20.5%, 22.5% and 104.5% respectively from those of the Al–Cu matrix alloy (303MPa, 485MPa and 6.6%).