This paper reviews the international literature on the natural enemies ofDreissenaspp. and discusses the biology and ecology of organisms known to be involved in their predation (176 species), parasitism (34 species), and competitive exclusion (10 species). Research on natural enemies, both in Europe and North America, has focused on predators, particularly birds (36 species) and fish (15 and 38 species eating veligers and attached mussels, respectively). Other field‐documented predation includes consumption of pelagic larvae by copepods and coelenterates, and consumption of attached mussels by leeches, crabs, crayfish, and rodents. Cannibalism of veligers by adult zebra mussels has also been reported. Ciliates and trematodes are the most commonly reported obligate parasites, with occasional records of suspected bacterial or ascetosporan infection. Mites, nematodes, leeches, chironomids, and oligochaetes have been observed to be associated symbiotically within the mantle cavity, but with few to no adverse effects. Organisms capable of competitively displacing zebra mussels from hard substrates include sponges, amphipods, algae, bryozoans, hydrozoan coelenterates, and other bivalve species (including interspecific competition amongDreissenaspp.).