The synthesis of ultrafine zinc oxide powders using the combination of precipitation and mechanical milling followed by subsequent heat treatment was investigated. Zinc hydroxide/oxidehydrate precursor was prepared by precipitation process using zinc chloride as the starting material. Sodium chloride was added to avoid agglomeration during the mechanical milling process. Zinc oxide particles were formed in the NaCl matrix after heat treatment and obtained after removal of NaCl. The size and structure of zinc oxide powders were studied using X-ray diffraction, transmission electron microscopy, and BET surface area measurements and thermal analysis. This has shown that the particle size of zinc oxide powder is strongly dependent on the weight ratio of sodium chloride and precursor. ZnO particles with an average primary particle size of 15 nm could be obtained when the NaCl/precursor weight ratio was 4 : 1 or above.