Oxides of manganese have large number of applications in the field of sensors, piezoelectric crystals etc. In the present work, Mn 3 O 4 nano materials were synthesized by using manganese acetate, adopting the method of thermal decomposition. The Nano materials thus prepared were characterized by employing various techniques like PXRD, FTIR, UV and Thermal analyses. The average particle size, calculated using Debye-Scherrer formula, was found to be in the range of 51 -62 nm. The presence of Mn 3 O 4 is also confirmed from FTIR. Thermal studies were also carried out. The optical band gap for the prepared nano materials was obtained from the UV-spectroscopic studies.