Cadmium oxide (CdO) nanoparticles were prepared starting from organometallic cis-[dmphen-CdI₂] complex (dmphen = 2,9-Dimethyl-1,10-phenanthroline) through one step calcination process at 800 ^oC, the thermal behavior of the complex during calcination was recorded by TGA/DTA. The obtained product are analyzed by FT-IR, UV-visible, X-ray diffractometer (XRD), EDS, SEM and TEM, the average size of CdO nanoparticles found to be 50 nm.