This study investigated the effects of trace moisture in hydrogen gas on the tribological behavior of carbon fiber (CF)-filled polytetrafluoroethylene (PTFE) composites by examining 20   wt% polyacrylonitrile-based CF-reinforced PTFE composites against stainless-steel disks in gaseous hydrogen environments, where moisture content was controlled at 1, 10, 20, and 40 ppm. The results revealed tribological characteristics of the sliding couples were significantly affected by the moisture content. Wear rates of pin specimens tended to increase gradually with moisture content. Similarly, average coefficient of friction increased as moisture content increased from 1 to 20 ppm. However, it decreased upon further increasing the water content. Moreover, surface analyses of the formed tribofilms at varying moisture contents revealed significant variations in terms of the amount and structure.