In this study, the effect of polyethylene glycol on the particle size and morphology of Cu25W composite powder was investigated. For this purpose, commercial elemental copper and tungsten powders were milled in a planetary-type ball mill. Milling conditions, namely ball-to-powder weight ratio and milling speed, were selected to be 10:1 and 300 rpm, respectively. In order to avoid agglomeration and to decrease the tendency of cold welding among powder particles, polyethylene glycol at the amount of 2 wt% was used as a process control agent. Morphological evolution of milled powders was investigated using scanning electron microscopy. In addition, the variation of particle size as a function of milling duration was examined using laser diffraction analysis. It was found that powder particle size gradually decreased with increasing milling duration. However, compared to the powder mixture without the process control agent, the powder mixture containing polyethylene glycol tends to lower the milling duration to achieve the same amount of particle size reduction. As a result of this effort, the usage of polyethylene glycol as a process control agent was found to be effective to obtain a composite powder with smaller particle sizes, especially in the earlier stages of milling process.