Protozoa cause many diseases such as leishmaniasis, giardiasis, amebiasis, trichomoniasis and Chagas disease. Metronidazole is the most commonly used drug in antiprotozoal therapy, but metronidazole, as well as other antiprotozoal drugs, can have several secondary effects. Essential oils have been successfully used in the treatment of diseases caused by protozoa. This is a review covering such research from the last 10 years. The main essential oils from 42 plant species demonstrate activity against protozoa, and those from the Lamiaceae family were the most studied with 16 species showing antiprotozoal effects. Other plant families containing species that demonstrate therapeutic effects include Verbenaceae with seven species, Asteraceae with four, Piperaceae with three and Annonaceae with two; the others nine families each had one species. Thymol was the main component found in eight species, followed by eugenol and terpinen-4-ol, which were found in four species, and carvacrol and camphor, which were identified in three and two species, respectively. Key words: Essential oil, diseases, Protozoa.