In situ spectroscopic ellipsometry was used to investigate the electrochemical precipitation of nickel hydroxide films. By use of optical models for inhomogeneous films it was found that a specific precipitation current density produced the most compact and homogeneous film structures. The density of nickel hydroxide films was derived to be 1.25-1.50 g/cm3. The redox behavior of precipitated nickel hydroxide films was studied with an effective-medium optical model. Incomplete conversion to nickel oxyhydroxide and a reduction in film thickness were found during the oxidation cycle.