Ti-6Al-4V titanium alloy has great application in medicine and military industries due to its capabilities, namely high strength to weight ratio and corrosion resistance. In the current research, the effect of aging treatment on microstructure and wear behavior of Ti-6Al-4V titanium alloy was investigated. Pin on disk wear test was applied to assess the wear behavior. Specimens were first solution treated at 950oC and 1050oC and then were quenched and aged. Some specimens were annealed before aging at 700oC. The results showed that aging treatment resulted in the hardness increase and the wear resistance decrease. It was also observed that annealing treatment before aging, enhanced the martensite decomposition and the formation of a2 particles, and correspondingly resulted in more hardness and lower wear resistance. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses confirmed that presence of hard phase a2 particles within soft beta phase was the main reason for wear resistance decrease.