Background: Leishmaniasis is a stigmatic and mutilating disease due to pathogenic species of the genus Leishmania which, depending on the species and the individual's immune status, may vary clinically from a cutaneous, mucosal, and visceral form, and for which there is no suitable treatment without significant side effects. Objectives: To measure the effect of ethanolic and aqueous extracts of Psidium guajava against axenic promastigotes and amastigotes of Leishmania spp. Methods: The method of [3-(3,4 -dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide] was used to study the antiparasitic effects of ethanolic (100mg/mL) and aqueous (100mg/mL) extracts of Psidium guajava on axenic amastigotes cultures (8.1 x103 parasite/mL) and promastigotes (12 x 104 parasite/mL) obtained from a patient with cutaneous leishmaniasis, and the percentage of parasite death was evaluated in comparison with Glucantime (300mg/mL) and untreated parasite cultures. Results: Regarding parasite death in promastigotes, the ethanolic and aqueous extracts had a percentage of 22.58% and -45.16%, respectively, with no significant difference between treatments (N=3) (p= 0.058). In contrast, the ethanolic and aqueous extracts had an antiparasitic percentage of 91.67% and -70.83%, respectively, with a significant difference between treatments (N=3) (p<0.05). Conclusions: Our study showed high and significant effectiveness in parasite death (91.67%) of Leishmania axenic amastigotes of the ethanolic extract (100mg/mL) of Psidium guajava, being this result promising and the basis for in vivo studies, using the ethanolic extraction of P. guajava.