In this work, the synthesis of manganese oxide nanoparticles was achieved by one-step spray pyrolysis method. The nanoparticles were synthesized just from MnCl2 aqueous solution. The solution was nebulized to a Si substrate placed at 400 °C for 1, 5 10 and 20 min and transported at a 0.1 L /min rate in a Nitrogen flux. The X-ray diffraction confirms tetragonal Mn3O4 as the unique phase in the whole sample. The scanning electron microscopy images proved the achievement of irregular nanoparticles with an average diameter of 280 nm experimentally determined by dynamic light scattering. Energy dispersive X-ray and Raman spectroscopy confirmed that the nanoparticles were obtained with Mn3O4 single-phase and the employed methodology prevented any contamination. The nanoparticles proved to induce temperature enhancement on artificial breast tissue by exposition to microwave radiation by achieving an increase in temperature around 8%.