Parasitic diseases represent a serious global problem and directly affect the health and quality of life of the population. Mansoa alliacea is a bignoniaceae found mainly in the Brazilian forests, known as “cipó-de-alho”, that means garlic vine, because of the strong odor of garlic exhaled when its parts are macerated. It is a plant used in folk medicine, with reports of various biological activities (anti-inflammatory, antifungal, antimicrobial and antioxidant). The present study aimed to characterize the essential oil of M. alliacea and evaluate its activity on Leishmania amazonensis and Caenorhabditis elegans. The essential oil was obtained by hydrodistillation, its chemical composition was analyzed by GC-MS and quantified by GC-FID. Leishmanicidal activity was performed on intracellular amastigotes of L .amazonensis using canine macrophages DH82, activity was measured using Enzyme Linked Immuno Sorbent Assay (ELISA). The nematicidal activity was evaluated on larvae of the nematode C. elegans model by means of the evaluation of motility. The oil cytotoxicity was evaluated on DH82 macrophages by colorimetric tetrazolium salt (MTT) assay. The concentrations tested were 0.1; 1; 10; 100; 1000 μg/mL. The drugs used as positive controls were: tetravalent antimony in anti-leishmania activity and ivermectin for anti-nematode activity. The GC-MS analysis of the oil showed the presence of organosulfur compounds with the following composition: allyl methyl disulfide (2.4%), diallyl tetrasulfide (3.4%) diallyl disulfide (36.6%), diallyl trisulfide (53.3%). The oil had excellent leishmanicidal activity, presenting an IC50 of 9.4 μg /mL, value 5 times lower than antimony (IC50 53 μg/mL). The cytotoxic dose (CC50) of the oil was 90.7 μg/mL, whereas antimony was CC50 = 1.7 μg/mL. The selectivity index (reason between CC50/IC50) of the oil was 10 and the antimony III was 0.03, demonstrates a low cytotoxicity of the oil. The oil was also efficient in paralyzing the larvae of C. elegans (IC50 = 113 µg/mL), already at the concentration 1000 μg / mL, was able to paralyze 94.65% of the larvae, value that did not differ from ivermectin (92.2%) at the same concentration. The inedited results, presented here, demonstrate the potential of M. alliacea in the development of new drugs for the treatment of leishmaniasis and nematodes, as it showed good activity and low toxicity. However, studies are needed and are ongoing in our laboratory to confirm the pharmacological potential of M. alliacea oil.