The passive and transpassive films on a Ni electrode have been studied by UV‐visible potential‐modulated reflectance (PMR) spectroscopy over a wide range of pH—1–14—and polarization potentials. PMR is a very sensitive in situ technique, although an established interpretation theory is still lacking for the results obtained with anodic oxide films. Here we follow the criterion that the PMR maxima of the films correspond to absorption edges of compounds present in them. The PMR results indicate that is present in the passive and transpassive film, both in acid and alkaline media. Two higher Ni oxides are also present in the transpassive film in alkaline media, but they could not be identified, owing to the existing confusion about bulk Ni higher oxides.