Wien’s displacement law has an important part in the development of modern quantum theory, and predicting it was one of the triumphs of Planck’s distribution law. It is usually expressed in terms of wavelength. Less known, however, is its expression in terms of frequency. Here, we derive Wien’s law as a function of frequency and point out its major predictive difference from the more common version. This version of Wien’s law would be a useful demonstration of a change in variables for a physical chemistry lecture course and the differences in predictions upon variable change.