The present study deals with the pharmacognostic and phytochemical studies of leaves of Ocimum americanum. It includes collection, identification, microscopical and phytochemical evaluation of leaves of O. americanum. The preliminary phytochemical studies indicate the presence of volatile oils, flavonoids, carbohydrates, phytosterols, tannins and fixed oils. The sections were taken and cellular structures were studied. The T.S of leaf shows the presence of epidermis, parenchymatous cells, collateral vascular bundle, lateral vein, glandular trichomes which are peltate type and sessile. Powder microscopy of the leaf shows the presence of epidermal peelings and multicellular unbranched trichomes.