This article reviews the international literature on the natural enemies of Dreissena spp.—bivalves which internationally have strong impacts on aquatic ecosystems, industries, fisheries, and aquaculture. It represents a revised edition of the initial treatment on this topic published over two decades ago, and as in the previous publication, it reviews the biology and ecology of organisms known to be involved in the predation (143 species), parasitism and commensalism (86 species and higher taxa), and competitive exclusion (14 species) of species in the genus Dreissena. Predators can at times have major impacts on dreissenid populations, but these reductions are typically only temporal and in restricted (e.g., shallow) areas within large waterbodies. A cumulative effect of a growing suite of enemies may have a constant, but overall limited, role in suppressing Dreissena densities—one far from any likelihood of population eradication. A diverse and abundant community of natural enemies, however, is beneficial because of its positive impact on energy flow. The introduction of dreissenids has redirected energy from the planktonic to the benthic community and predators, in particular molluscivorous fish and waterfowl, have served to redistribute this energy flow back into the pelagic environment.