Polyphenylene oxide (PPO) films electrochemically deposited on highly oriented pyrolytic graphite (HOPG) have been investigated by spectroscopic ellipsometry (SE) and atomic force microscopy (AFM). The optical properties of the substrate and film were measured over the visible and near UV spectral ranges. PPO film thicknesses were deduced from SE measurements and compared to results obtained by AFM. Spin cast linear PPO films were also measured. We demonstrate the AFM measurements are concordant with and useful for the interpretation of the ellipsometric measurements. The refractive index in the visible light region for the electrodeposited PPO films is 1.721 - i0.006 and for the linear PPO films is 1.698 - i0.028.