Pentalinon andrieuxii Muell Arg is a Mexican-Central American plant anciently used by local people to treat cutaneous leishmaniasis. We evaluated a hexane extract of the root we called PAE for its chemical content and for its immunochemical and in vitro activity against Leishmania donovani and healing of experimental Kala-azar. Chemical analysis using gas chromatography coupled to mass spectrometry (GC-MS) identified hexadecanoic acid, hexadecanoic acid ethyl ester, 9, 12-octadecadienoic acid ethyl ester, octadecanoic acid ethyl ester, 9-octadecenoic acid ethyl ester and diethyl phthalate as the main compounds present in PAE. We also demonstrated PAE kills promastigotes and amastigotes in vitro and significantly reduces parasite loads in liver and spleen of infected Balb/c mice. PAE induces expression of NFkB/AP-1 transcription factors and production of IL-2 and IFN-γ by spleen cells of PAE treated but not in the untreated control mice. Furthermore, there were not IL-6, IL-10 nor TNF production in macrophages treated in vitro with PAE. We developed an affordable extract of P. andrieuxii effective to treat experimental Kala-azar in Balb/c mice.