When resources are economically defendable, interspecific aggression may occur when one species attempts to use the defended resources to the detriment of the defending species. In the Florida Keys, we investigated vigorous and frequently observed aggression between the Redband Parrotfish, Sparisoma aurofrenatum, and the Redtail Parrotfish, Sparisoma chrysopterum, along with microhabitat overlap and foraging overlap. Sparisoma chrysopterum home ranges extensively overlap S. aurofrenatum territories. Both parrotfishes are found over and feed upon Halimeda opuntia, a green calcareous alga, significantly more than all other microhabitats. Interspecific aggression by these parrotfishes is primarily directed toward confamilials. Extensive overlap in distributions combined with overlap in microhabitat and foraging behavior likely play a role in fostering the disproportionately high interspecific aggression observed between these two parrotfishes in the Florida Keys.