This work discusses the polarization of nonuniform plane waves (NPWs). A NPW can be created when a uniform plane wave is transmitted from a lossless medium into a lossy medium at an oblique angle. When a linearly polarized wave is transmitted into a lossy medium, the in-plane field transitions to elliptical polarization while the transverse field remains linearly polarized. This is a completely different behavior of a polarized wave compared to those that are created by introducing a phase difference between two perpendicularly polarized waves, where the polarization of both electric and magnetic fields changes together. The zero-divergence restriction determines the rotation direction of the NPW’s elliptical polarization.