Objective: To compare the in vitro antiparasitic activity of aqueous extracts from Ziziphus joazeiro leaves and stem bark against Trypanosoma cruzi, Leishmania braziliensis, and Leishmania infantum, as well as to evaluate its cytotoxicity in mammalian cells, in addition to identifying the chemical composition of the extracts. Methods: Ziziphus joazeiro leaf and stem bark aqueous extracts were prepared by cold extraction maceration and subjected to ultra-efficient liquid chromatography coupled to a quadrupole/time of flight system. The susceptibility assays used Trypanosoma cruzi CL-B5 strains and promastigote forms of Leishmania braziliensis and Leishmania infantum for antiparasitic activity of the extracts. Moreover, mammalian fibroblasts NCTC clone 929 were used for cytotoxicity analysis. Results: Terpenoid compounds, flavonoids and phenolic acid were identified in extracts. The stem bark aqueous extracts presented more significant results in terms of antiparasitic activity compared with the leaf aqueous extracts, especially against Leishmania braziliensis and Leishmania infantum promastigote forms with an IC50 < 500 μg/mL. The cytotoxicity evaluation showed moderate toxicity of the stem bark aqueous extracts, which is relevant information for the rational use of this plant part since it is widely used by the population. Conclusions: These preliminary results may contribute to the formulation of new therapeutic agents against this group of neglected diseases, so further investigations are required to delineate the mechanisms of action mainly of the aqueous extract of stem bark of Ziziphus joazeiro.