Current research is focused on synthesis of sustainable and environment friendly process of particles for effluent treatment applications. To further enhance the prospects of eco-friendly approach, the current study is dedicated to the green synthesis of Manganese dioxide microparticles that has a wide range of applications from waste water treatment, heavy metal remediation to electronic applications. A procedure to obtain the Manganese dioxide particles from Brassica oleracea (cabbage) leaves has been devised. Effect of initial KMnO4 concentration, amount of Brassica oleracea (cabbage) leaves extract, pH and temperature of the solution was evaluated. The obtained Manganese oxide particles were characterized using Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray (EDX) and X-Ray Diffraction (XRD). The particle size was found to be in the range of 10-20 µm with 15.98% Manganese content. The X-ray diffraction revealed the presence of tetragonal MnO2 crystals (Pyrolusite) and the sample peaks on the diffraction graph coincided with the peaks for Manganese (IV) oxide.