Many species of oomycetes cause economic and environmental damage owing to their ability to infect a range of plants and animals. Although research on plant pathogenic oomycetes has flourished in recent years, the animal pathogenic oomycetes have received less attention. This is unfortunate because several species are responsible for devastating diseases in aquaculture and natural ecosystems and proper treatments are not available or are limited. Therefore, momentum is being created to revive research into this neglected group of pathogens. Here, we discuss the latest developments in our current understanding of the biology, host-pathogen interactions and environmental and economical impact of the animal pathogenic oomycetes and review the recent advances in this emerging field.