In this study, the effect of mechanical alloying parameters, namely the effect of process control agent, ball-to-powder weight ratio and milling duration, on the synthesis of Cu25W composite powder was investigated. Planetary-type ball milling equipment was used to conduct mechanical alloying experiments. Stearic acid was used as the process control agent in order to establish a balance between cold welding and fracturing. The optimum amount of stearic acid was determined as a function of particle size and milling time at constant speed. By using this optimum amount of process control agent, three different ball-to-powder weight ratio values were also employed, and the effect of ball-to-powder weight ratio on particle size and morphology of Cu25W composite powders was investigated. The microstructural evolution of the milled powders was characterized using scanning electron microscopy and laser diffraction analysis. The test results have shown that the morphology and particle size distribution of the milled powders change significantly depending upon the milling parameters. In addition, higher ball-to-powder weight ratio values tend to lower the milling duration for the same amount of particle size reduction. However, particle size reduction suffers beyond the maximal value of ball-to-powder weight ratio, especially in the later stages of mechanical alloying.