Green synthesis of metallic nanoparticles using plant sources has become an excellent substitute for conventional chemical synthetic methods. Nowadays, nano biotechnology is growing at a very fast rate due to its various possible application in the pharmaceutical biomedical, textile, paper industries. In our study, we have reported the green synthesis of chalcogenide nanostructure pharmacologically active chromium oxide (Cr2O3) nanoparticles using synthesized chromium (III) complex as a single route precursor. The synthesized chromium (III) complex was reacted with an aqueous extract of cinnamon bark for the green synthesis of Cr2O3 nanoparticles. In the present study, we aimed to synthesize chromium oxide nanoparticles (Cr2O3 NPs) through a facile low-cost, eco-friendly route. In this method, we use the aqueous environment for green synthesize of Cr2O3 NPs because the use of an aqueous medium plays a very important role in reducing time, reducing minimum possibilities of side reactions and proper execution of conversions of synthesized Cr(III) complex into a good quality of Cr2O3 NPs in a very less time. The synthesized chromium (III) complex and green synthesized Cr2O3 NPs were thoroughly analyzed through various structural, morphological, electronic, vibrational and pharmacological characterization techniques. Powdered X-ray diffraction studies confirm the formation of well-defined equip spaced crystalline nanoparticles of chromium oxide. Transmission electron microscopy exhibits oval-shaped structure of Cr2O3 NPs with an average particle size of 48 nm. Sharp electronic absorptions ends at 345nm for Cr(III) complex and at 429nm indicates the synthesis of good quality of chromium(III) complex and Cr2O3 NPs. The FT-IR spectral studies confirmed the presence of Cr-O stretching, N-H bonding and C=O stretching vibrations in synthesized Cr(III) complex was performed to investigate the thermal stability of the complex. The Cr(III) complex is stable up to 350ºC. The effective pharmacological activities like in vitro antimicrobial and antioxidant activities explained the presence of strong electron-withdrawing and electronwithdrawing groups in synthesized chromium (III) complex. The green synthesis of Cr2O3 NPs via aqueous extract of cinnamon back in proper stoichiometric ratio is a good method for synthesizing highly effective bioactive agents which will be considered as a good drug candidate for various biological applications in future for various biomedical applications