The Oomycete genus Phytophthora is one of the most destructive plant pathogens. Over 100 Phytophthora species are described to date, but only a few are of major economic concern to the cacao industry. The history, biology, and control of Phytophthora spp. affecting cacao worldwide are examined. The genetic diversity, symptomatology, control measures, and screening for resistance of these pathogens are reviewed. The Phytophthora species attacking cacao were distributed across four of the ten clades recognised, and of these P. palmivora is ubiquitous to the cacao-growing regions. Although highly destructive, the genetic diversity within each species that attack cacao appeared to be limited, with many clonal lineages being recognised. Free water is needed for dispersal, infection, and completion of the life cycle of Phytophthora. The typical life cycle of Phytophthora is elucidated and illustrated. Infection on cacao is usually by motile, biflagellate zoospores which are liberated from stalked sporangia. Hyphae grow inter- and intracellularly and result in necrosis of host tissues. Various methods devised for the control of the disease and their relative merits are discussed. Screening methods for the identification of resistance are evaluated and their importance to future breeding programmes to generate stable resistant cultivars is discussed. Reliable high-quality disease resistance data for genomic applications will be increasingly needed. This data is dependent on robust screening methods and guidelines for future direction of research are also outlined.