Model terrestrial ecosystems were set-up in the Ecotron controlled environment facility. The effects of elevated CO₂ (ambient + 200 mol/mol) and temperature (ambient + 2.0°C) on plant chemistry, the abundance of the peach potato aphid Myzus persicae, and on the performance of one of its parasitoids Aphidius matricariae, were studied. Total above-ground plant biomass at the end of the experiment was not affected by elevated atmospheric CO₂, nor were foliar nitrogen and carbon concentrations. Elevated temperature decreased final plant biomass while leaf nitrogen concentrations increased. Aphid abundance was enhanced by both the␣CO₂ and temperature treatment. Parasitism rates remained unchanged in elevated CO₂, but showed an increasing trend in conditions of elevated temperature. Our results suggest that M. persicae, an important pest of many crops, might increase its abundance under conditions of climate change.