Discarded vehicle tires degrade to leach toxins into collected rainwater that provides habitat for competing mosquito species. We tested the hypothesis that more degraded tires that contain greater tire leachate alter interspecific mosquito competition, producing a condition-specific advantage for the competitively inferior resident, Culexpipiens, by relaxing the effects of competition with the invasive Aedes albopictus. Varying densities of newly hatched Ae. albopictus and Cx. pipiens larvae were added to tires that had been exposed to different ultra-violet (UV)-B conditions that mimicked either full-sun, shade, or no UV-B conditions in the field. There were higher competitive effects of Cx. pipiens on the population performance and survival of Ae. albopictus in tires exposed to shade and full-sun UV conditions that had higher concentrations of zinc, a marker contaminant of tire leachate. Zinc concentration was also higher in Ae. albopictus than Cx. pipiens indicating greater exposure of the invasive species to tire leachate. These results indicate that tire leachate can affect the outcome of the competition between Ae. albopictus and Cx. pipiens, helping foster the regional persistence of the resident Cx. pipiens. Cx. pipiens is the main vector circulating West Nile virus (WNv) within avian populations in many cities in the northern United States. Ae. albopictus may play an important role in WNv transmission, bridging the virus from avian into human populations. Increased coexistence of these two species resulting from condition-specific competition in tire habitats may increase WNV transmission risk.