This review discusses the current knowledge of the phytochemistry and in vitro and in vivo evaluations carried out using the extracts and, where appropriate, the main active components isolated from the genus Bougainvillea. Out of 18 species, most phytochemical, pharmacological, and toxicological studies focused on four species with different cultivars and one hybrid. Some plants are used for the treatment of various health disorders. Numerous phytochemical investigations of plants in this genus confirm the presence of aliphatic hydrocarbons, fatty acids, fatty alcohols, volatile compounds, phenolic compounds, peltogynoids, flavonoids, phytosterols, terpenes, carbohydrates, and betalains. Various studies have confirmed that these extracts or active substances that were isolated from the genus Bougainvillea have multiple pharmacological activities. Some species of Bougainvillea have emerged as sources of traditional medicine in human health. More studies of the phytochemical, pharmacological, and toxicological properties and their mechanisms of action, safety, and efficacy in all Bougainvillea species, cultivars, and hybrids are advisable for future research.