Aboveground consumers are believed to affect ecosystem functioning by regulating the quantity and quality of plant-litter entering the soil. We uncover a novel pathway whereby terrestrial predators regulate ecosystem processes via indirect control over soil community function. Grasshopper herbivores stressed by spider predators have a higher body carbon-to-nitrogen ratio than grasshoppers raised without spiders. This change in elemental content does not slow grasshopper decomposition but perturbs belowground community function, decelerating subsequent decomposition of plant-litter. This legacy effect of predation on soil community function appears to be regulated by the amount of herbivore-protein entering soil.