An organometallic catalytic agent ([(Hexyl)4N]3FeCl3Br3) has been synthesized through the reaction of tetrahexylammonium bromide ((Hexyl)4NBr) and iron chloride (FeCl3) aqueous solutions. Multi-walled carbon nanotubes (MWCNTs) were obtained by spray pyrolysis of toluene (carbon source) using the new organometallic compound as catalyst. The synthesized catalytic agent was characterized by ultraviolet-visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FTIR), and thermal analysis (TA) techniques. Spectroscopic results indicated that the new iron organometallic compound has suitable characteristics to grow MWCNTs by spray pyrolysis. The MWCNTs were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques. The MWCNTs grow in a disordered way without orientation with diameters ranging from 20 to 50 nanometers. XRD patterns exhibit the 2-H graphite characteristics peaks of the MWCNTs.