A simple and cost effective method using a thermal oxidation process for synthesizing cupric oxide (CuO) nanostructures is demonstrated in this paper. Using elevated temperatures ranging from 100°C to 400°C, the optimum formation of CuO composition indicated by an X-ray diffraction (XRD) was obtained at 400°C. Then, the effects of gas flow rates (ranging from 1 to 10 kPa) on the formation of CuO nanorods were investigated using a field emission scanning electron microscope (FESEM). It was found that at higher gas flow rate, the formation of CuO nanorods was obviously observed. The current-voltage (I-V) characteristic obtained from an I-V measurement system shows that diode characteristic has been formed with threshold voltage (Vth) of 0.9 V and breakdown voltage (VB) of-5 V. The mechanism of structural changes will be discussed in details.