Polyurethane (PU) samples were immersed in a 1 M HCl solution for different durations from 0 to 90 days to investigate the influence of immersion time on the tribological performance of the samples. The effects of thermal, mechanical, and surface properties of the PU on its tribological performance were also investigated with respect to immersion time. It was found that the friction coefficient of the PU measured against a steel ball significantly decreased with increased immersion time due to the lubricating and cooling effects of absorbed water in the PU during the immersion. The decreased friction of the PU led to the improved wear resistance of the polymer, though the mechanical strength of the PU was reduced by the prolonged immersion due to the increased plasticization of the polymer. The experimental results clearly indicated that the immersion of the PU in the acidic solution for a certain period significantly influenced the tribological performance of the polymer.