Abstract: Core–shell silver–zinc oxide nanoparticles (Ag: ZnO NPs) were synthesized utilizing the plasma jet method, then characterized by ransmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and UV-Visible spectroscopy. XRD confirmed crystalline peaks at 38.45°, 44.39°, 64.57° and 77.47° (planes 111, 200, 220 and 311), with particle sizes below 100 nm. Using UV-Visible spectroscopy, Ag: Zn NPs were confirmed with absorption peaks at 374 nm and 454 nm for Ag: ZnO NPs. After 100% Ag: ZnO NP exposure over the course of 48 h, 61% inhibition of growth was observed within the MDA cells, while toxic effects were experienced by the Rat Embryonic Fibroblast (REF) normal cell population, with only 18.16%. The antiparasitic properties of Ag: Zn NPs demonstrated 62.3% inhibition of Leishmania Tropica and 55% inhibition of Donovani Leishmania. The findings suggest that Ag: Zn NPs have selective cytotoxic effects against cancerous and parasitic cells, thus representing a new class of cytotoxic agents.