The α-proteobacterium Wolbachia is an intracellular endosymbiont of many insects and other invertebrates. Aedes albopictus, naturally infected with Wolbachia, is an effective invasive species. We investigated intraspecific competition among Ae. albopictus larvae with and without Wolbachia infections. The intensity of larval competition (as a function of larval density) had significantly more impact upon larval performance than endosymbiont infection status. Wolbachia differentially influenced competition by male and female larvae and, at least at low larval densities, provided competitive advantages to infected larvae relative to uninfected larvae. Our results provide evidence for overall fitness effects upon Wolbachia-infected Ae. albopictus larvae that may partially explain invasion of Ae. albopictus by Wolbachia plus the observed widespread competitive displacement of native container-breeding mosquitoes by this species.