Palladium oxide thin films are studied by ellipsometry, optical transmission, and Raman scattering. The PdO films are made by completely oxidizing Pd films sputtered onto fused silica substrates, and their optical constants determined using a combination of ellipsometry and transmission measurements. Oxidation kinetics experiments are performed on thick Pd substrates at temperatures of 300–500 °C. The optical properties of the films show a thickness dependence suggesting an increased absorption at the PdO-Pd interface. Ellipsometry on oriented single crystals of PdO yields the anisotropic optical constants at 632.8 nm. These results are combined with an effective medium theory to show that the oxidized films have a void density of 20–25%. Raman scattering is demonstrated to be a very sensitive probe for detecting the presence of PdO on Pd. An oxide only a few Å thick is readily detectable, despite the absence of any surface enhanced Raman effect.