Trophic studies can provide valuable information on the risk an invader poses to native species. Brook Stickleback Culaea inconstans is an invasive fish species in Wyoming whose effect on native fish assemblages is poorly understood. Our goal was to understand the potential for competitive interactions between Brook Stickleback and native fishes. We used stable isotopes of carbon (ẟ13C) and nitrogen (ẟ15N) to evaluate the feeding ecology of Brook Stickleback relative to four native fishes. The data are appropriate for exploring whether native fish isotopic niches changed in sympatry with Brook Stickleback and to evaluate niche overlap between native fishes and Brook Stickleback. The data are associated with the manuscript: Ruthven, J.S. and A.W. Walters. In review. Invasive Brook Stickleback Culaea inconstans minimally alters the trophic ecology of four native fishes in Wyoming, USA. Food Webs.