Eastern Mosquitofish (Gambusia holbrooki) is an invasive and globally widespread species that is considered highly tolerant. We used species distribution models (SDMs) to assess factors, including the role of anthropogenic perturbation, that mediate its invasion on a regional scale. A better understanding of the important large-scale factors may help us identify future areas of concern and potential avenues for control. We built SDMs from presence records and randomly selected pseudo-absences of mosquitofish on a 10- × 10-km grid. We used 10 modeling techniques implemented in the biomod2 software and ensemble forecasts. Final models contained 12 environmental predictors, including natural environmental factors (elevation, slope, topographic index, precipitation, accumulated flow, temperature mean and range) and anthropogenic perturbation indicators (population density, urban and agricultural land uses, number of local and upstream dams). Elevation, temperature, and accumulated flow most strongly influenced mosquitofish distribution, and mosquitofish were found more frequently in downstream, warmer waters. Anthropogenic features, except the number of upstream dams, were poorer predictors of mosquitofish presence than were natural environmental factors. The best models suggested that mosquitofish are more likely to occur in areas with more dams upstream, but removing this predictor did not strongly affect model results. Restoration efforts or modifications to anthropogenic features appear unlikely to alter mosquitofish distribution patterns, highlighting the importance of preventing introductions to new areas. Mosquitofish have been extensively documented in the Iberian Peninsula, but consensus methods suggest many additional suitable areas from which records were not found. Thus, this highly invasive species is or may become much more widely distributed than current observations in the region.