Abstract: The aim of this research was to study the pharmacognostic parameters of leaves of Ocimum gratissimum L. (family: Lamiaceae). Macroscopic study showed that the leaves of this plant possess dark green color with characteristic aromatic odour and bitter taste. Powder microscopy showed the presence of numerous glandular simple trichomes of average length 101 μm and anomocytic stomata were also present, whereas, T.S of leaf showed that the leaf has a pot shape midrib and a thin lamina with uneven lower epidermis attached at the lateral sides of its upper side leaving a concave central dorsal depression. Both upper and lower epidermis showed simple, covering, uniseriate trichomes as well as sessile short stalked glandular trichomes. Quantitative microscopy viz., veinlet termination number, vein islet number, stomatal number, stomatal index; physico-chemical parameters viz., ash values, extractive values, Thin layer chromatography (TLC); florescence analysis of Ocimum gratissimum L. were also been determined. TLC studies showed the presence of various phytochemicals in the extracts. Qualitative phytochemical analysis revealed the presence of alkaloids, tannins, flavonoids, terpenoids (methanolic, ethanolic extracts); alkaloids, flavonoids and terpenoids (petroleum ether, chloroform extracts) and carbohydrates in alcoholic extract. This is the first such study on standardization of Occimum gratissimum L. leaf which would serve as a standard reference for identification and distinguishing the plant from its adulterants.