A novel approximate uniform geometrical theory of diffraction (UTD) for analyzing an electromagnetic wave diffracted by a planar material junction on PEC ground plane has been developed in this research. The proposed UTD solution is based on an ansatz obtained from the Weiner–Hopf (W–H) solution by approximating the W–H split functions. This makes the proposed UTD solution to be a relatively simple and closed form expression. Additionally, the proposed UTD solution can deal with both a planar material junction on PEC ground plane and a two-part problem with any types of wave illumination such as a plane wave, a cylindrical wave, and a spherical wave. The accuracy of the proposed UTD solution is compared with the W–H solution and finite different time domain (FDTD) which provides very good agreement. The proposed UTD solution has very small numerical errors. However, the accuracy of the proposed UTD solution is good enough for engineering applications.