Two or more species cannot coexist on a single limiting resource in a constant environment unless each species can increase when rare. In this paper, we show, theoretically and empirically, how trade-offs in life history characters have the potential to mitigate the effects of interspecific competition and promote persistence in a host-multiparasitoid interaction. Theoretically, we show how niche partitioning between competing parasitoids can arise through differences in resource breadth and utilization. We demonstrate, empirically, how trade-offs between parasitoid larval competitive ability and wasp life history characters (adult wasp longevity and the ability to paralyze hosts) can be mediated. Differences, not only in the mean, but also in the variance of these life history traits can influence the outcome of competition, and we discuss how species life history trade-offs can promote species coexistence. none