Tuberculosis (TB) is the main cause of morbidity in modern era and a latent infection affecting nearly one third of worldÃ¢â‚¬â„¢s population including forty percent from India. There is an urgent need to explore the effective and promising new antiÃ¢â‚¬â€œ tubercular drugs to combat against Tuberculosis. Nature provides diverse secondary metabolites with anti- tubercular activity in medicinal plants. Among them Allium cepa (onion)., contains various constituents like quercetin, fructose, quercetin-3-glucoside, isorhamnetin-4-glucoside, xylose, galactose, glucose, mannose, organosulfur compounds, allylsulfides, flavonoids, flavenols, S-alk(en)yl cysteine sulfoxides, cycloalliin, selenium, thiosulfinates, and sulfur and seleno compounds that have proved to have protective role in tuberculosis. Allium cepa (onion) possesses antibiotic activity against both Gram-positive and Gram-negative bacteria and can be used to prevent tuberculosis most effectively.