The round goby (Neogobius melanostomus) is a benthic, Ponto-Caspian fish introduced into the Great Lakes which has since secondarily invaded tributary streams and rivers. Various studies have shown they alter invertebrate communities, and these alterations have impacted organic matter decomposition. Stream studies suggest leaf litter decomposes less rapidly at sites where gobies are present compared to locations where they are absent. This study sought to determine whether the reduction in decomposition was a function of microbial community richness and diversity. In the present study, BIOLOG mulit-substrate plates were used to assess microbial community metabolism in conjunction with leaf litter decomposition rates at sites with and without gobies. Substrate consumption richness at the sample site without gobies was significantly less after 12-hours but significantly greater after 48-hours of incubation relative to the site with gobies. Average well color development (AWCD) was greater at the site without gobies compared to the site with gobies. ACWD data at 48-hours and substrate consumption richness suggest that sites without gobies have greater microbial community diversity compared to sites with gobies present. However, it also could suggest that the site without gobies favors faster growing microorganisms. Collectively these data suggest gobies may alter leaf litter decomposition by affecting microbial communities.