Green synthesis is an eco-friendly approach to nanoparticle production, which eliminates the use of toxic chemicals, high temperatures, and costly equipment needed for traditional physical and chemical synthesis methods. This eco-friendly approach was used in the present study to biosynthesize zinc oxide nanoparticles (ZnO NPs) from Mangifera indica (mango) leaves which were then evaluated for their antioxidant activity and cytotoxic effects on lung cancer A549 cells. Synthesized ZnO nanoparticles were characterized using UV-vis spectroscopy, XRD, SEM, and EDX analyses. The XRD and SEM analyses showed 45-60 nm as the size of synthesized nanoparticles, the pure crystal form of ZnO NPs, and the shape of the NPs as nearly spherical and hexagonal quartzite. The antioxidant potential of nanoparticles was estimated using a DPPH free radical scavenging assay. The percent of viable cells was inversely proportional to the concentration of ZnO nanoparticles at 25 mu g/mL concentration. The MTT assay used for cytotoxicity evaluation depicted the significant cytotoxic effect of ZnO NPs against the A549 lung cancer cell line. The drop in the proportion of viable A549 cells after exposure to ZnO NPs was comparable to the effects of the standard drug used i.e. cyclophosphamide. Antioxidant activity of NPs was increased by increasing the concentration of NPs. The present biosynthesis approach is rapid, inexpensive and eco-friendly and it yielded highly stable ZnO NPs with significant antioxidant and anticancer potential. This is the first report of M. indicia -mediated synthesis of ZnO NPs as antioxidant and, anticancer agents for the treatment of lung cancer and subsequent therapeutic applications.