Intraspecific variation is central to our understanding of evolution and population ecology, yet its consequences for community ecology are poorly understood. Animal personality—consistent individual differences in suites of behaviors – may be particularly important for trophic dynamics, where predator personality can determine activity rates and patterns of attack. We used mesocosms with aquatic food webs in which the top predator (dragonfly nymphs) varied in activity and subsequent attack rates on zooplankton, and tested the effects of predator personality. We found support for four hypotheses: 1) active predators disproportionately reduce the abundance of prey, 2) active predators select for predator-resistant prey species, 3) active predators strengthen trophic cascades (increase phytoplankton abundance), and 4) active predators are more likely to cannibalize one another, weakening all other trends when at high densities. These results suggest that intraspecific variation in predator personality is an important determinant of prey abundance, community composition, and trophic cascades.