To understand organismal response to rapidly change climate, many studies measure thermal tolerance in populations of single species. However, species do not exist in isolation, and their responses to novel climates will be determined by temperature-mediated interactions with other species. Thus, if interacting species differ in thermal sensitivity, shifts in community composition and dynamics will occur as environments warm. Still, studies that measure thermal tolerance in interacting species under similar conditions are rare. We examined how changing temperature could alter interactions between an insect host (leaf-mining caterpillar) and one of its major predators (wasp parasitoid). In the wild, adult wasps lay eggs on miners pupating in aspen leaves. After hatching, larval wasps consume the miner and eventually emerge as winged adults. Whether temperature mediates wasp–miner interactions remains unknown. We measured miner and wasp development rates across temperatures and thermal tolerance limits (CTmax, LT50). In the development experiment, aspen leaves containing leaf miner pupae and wasp eggs were held for 30 days in temperature-controlled incubators that mimicked cold, normal, and hot spring temperatures. Leaf miners developed and emerged as moths sooner than wasps in the coldest treatment (15 ºC), but later than wasps in the warmest treatment (35 ºC). In the heat tolerance experiments, caterpillars generally tended to be more tolerant than wasps. Our results suggest not only that thermal sensitivity varies between host and parasitoid, but which species ‘wins’ or ‘loses’ might depend on the life stage at which thermal stress occurs.