Green synthesis of cadmium oxide nanoparticles (CdO NPs) using leaves extract of Phoenix roebelenii as a novel natural reducing/stabilizing agent was reported for the first time. The structure, morphology and optical properties of the synthesized CdO NPs were studied by various physical techniques. X-rays diffraction (XRD) analysis provided evidence of single face centered cubic Monteponite phase of the CdO NPs. Selected area electron diffraction analysis (SAED) confirmed the crystalline structure of the synthesized sample. High resolution transmission electron microscopy (HRTEM) results showed spherical nanoparticles with an average diameter of 34.9 ± 0.4 nm. The isothermal behavior of CdO NPs was investigated by differential thermal analysis/thermogravimetric analysis (DTA/TGA) and the results confirmed the stability of the CdO NPs after calcination at 500 °C. The diffuse reflectance spectroscopy (DRS) indicated the presence of direct and indirect band gap with energy 2.39 and 1.91 eV respectively. Fourier Transform Infrared analysis (FTIR) showed the functional groups of bioactive compounds of Phoenix roebelenii leaves extract. Possible mechanism of interaction between these bioactive compounds and Cd precursor was proposed based on the FTIR results.