The controlled thermolysis of a presynthesized single precursor, Fe-3(CH3COO)(6)(OH)(2)CH3COO, in a closed reactor at 700 degrees C in ail inert atmosphere produced ferromagnetic Fe3O4 octahedra Without using solvent or catalyst. The octahedral shape with the 6-10 mu m diameter of Fe3O4 is realized using field emission scanning electron microscope, and the composition, with an attached energy dispersive X-ray analyzer. The single-crystalline face-centered Cubic Structure of Fe3O4 octahedra is analyzed by X-ray diffraction measurements, further Supported by Raman spectroscopy and transmission electron microscopy. The thermogravimetric analysis measured the amount of carbon present oil the Fe3O4 octahedra surfaces. The vibrating magnetometer corroborated ferromagnetic behavior of Fe3O4 octahedra with 150 Oe coercive force, 48 emu/g saturation magnetization, and 5 emu/g remnent magnetization.