Natural products are compounds extracted from plants, marine organisms, fungi or bacteria. Many researches for new drugs are based on these natural molecules, mainly by beneficial effects on health, health, efficacy, and therapeutic safety. Leishmaniosis, Chagas disease and African sleeping sickness are neglected diseases caused by the Leishmania and Trypanosoma ssp. parasites. These infections mainly affect population of developing countries; they have different symptoms, and may often lead to death. The therapeutic drugs available to treat these diseases are either obsolete, toxic, or have questionable efficacy, possibly through encountering resistance. Discovery of new, safe, effective, and affordable molecules is urgently needed. Natural organisms, as marine metabolites, alkaloids, flavonoids, steroids, terpene and coumarins provide innumerable molecules with the potential to treat these diseases. This study examines studies of natural bioactive compounds as antileishmanial and antitrypanosomal agents.