Design/methodology/approach A series of PEEK composites with UHMWPE contents ranging from 1.0 to 10.0 wt% were fabricated via hot pressing. The tribological performance of the samples under water-lubricated conditions was evaluated with a reciprocating wear tester. The wear surfaces were characterized in terms of both three-dimensional topography and micro-morphology. In addition, the effect of varying loads on the tribological behavior of the composites was investigated. Findings The friction coefficient and wear rate of PEEK composites initially decrease and then increase with increasing UHMWPE content. At a UHMWPE content of 3.0 wt%, the composites exhibit the lowest friction coefficient and wear rate, with reductions of 42% and 71%, respectively, compared to pure PEEK, along with a 44% reduction in worn surface roughness. Scanning electron microscope (SEM) analysis reveals that the wear surface of the 3.0 wt% UHMWPE-reinforced PEEK composite is smooth, whereas the surface of pure PEEK predominantly shows plastic deformation and adhesive wear. Originality/value This study reveals that incorporating low-content UHMWPE significantly enhances the tribological performance of PEEK in water-lubricated environments. These findings provide valuable insights for optimizing PEEK bearing performance and broadening its engineering applications under water-lubricated conditions.