The success of an invasive species becoming established in a new region often depends on its interactions with ecologically similar resident species. The propensity of the newly-established mosquito Aedes japonicus to inhabit rock pools throughout the eastern United States provides a natural setting for interspecific larval competition with the native Aedes atropalpus. A laboratory experiment conducted in simulated rock pools to evaluate larval interactions between and within these two species suggested that the performance of both species was more significantly impacted by intraspecific conditions than interspecific conditions of the same mosquito density. Aedes atropalpus was apparently more sensitive to larval densities than Ae. japonicus because it reproduces autogenously, requiring a lengthened period of larval development to obtain nutrient reserves for egg development, which may ultimately put Ae. atropalpus at a disadvantage under larval conditions of competition and limited resources. Excessively stressful experimental conditions, as evidenced by reduced body size, and thus fecundity and estimated finite rate of increase, may have obscured the effects of larval competition between these species. The impact of larval competition between these species in rock pool communities warrants further investigation under more ecologically realistic experimental conditions.