Aim: The purpose of this study is to determine the Pharmacognostic, phytochemical and physicochemical standardization of Pleurotus ostreatus. Materials and Methods: The disease-free oyster mushroom fruiting body was collected during the rainy season from Himgiree Hi-Tech Agro (Mushroom Division) Kalyani Nagar Pune. Their identity and authentication were done. Macromorphology, cytomorphology, powder microscopy, micrometry, physicochemical evaluation, and phytochemical screening were done according to the WHO guidelines and standard methods. Results: Macromorphology of mushroom structure has a broad, oyster or fan-shaped cap, spanning 2-35 cm. yellowish grey colour, chocolaty odor, and significant taste. Cytomorphology of mushroom shows different cells such as aciculate, sphaerodunculate, lanceolate thick-walled, utriform, cornuate, Subcapitate, mucronate, cornuate, clavate 4-sterigmate basidium and in powder microscopy nodulose, isodiametric, snout like pore, spiny, bullet shaped, cuboid. The preliminary phytochemical analysis of the mushroom shows the occurrence of active compounds such as flavonoid, tannin, glycoside, coumarin, phenols, steroid, terpenoids protein and amino acid. Conclusion: The results obtained in this study the Standardization of phytochemical, physico-chemical is a fundamental dimension for sample identification, quality, and purity of oyster mushroom (Pleurotus ostreatus).