The present investigation reports, the synthesis of manganese oxide (a-Mn2O3) nanobundles using ther- mal decomposition and its physicochemical characterization. The a-Mn2O3 nanobundles have been pre- pared using manganese oxalate dihydrate powders as precursor in the presence of oleylamine and triphenylphosphine as solvent and capping agent. Transmission electron microscopy (TEM) analysis demonstrated Mn2O3 nanobundles compose of nanospheres with diameter 30 nm. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT-IR) spectroscopy. Manganese oxide nanocrystals have been prepared under different condition. The controlled experimen- tal results showed that the use of oleylamine and triphenylphosphine as the solvent and capping agent in the chemical process played important role in the formation of the final products.