CuInP2S6 is a layered thiophosphate material characterized by photo-, ferrielectric, and ion-transport properties, which make it a promising candidate for applications in energy storage and electronic devices. This work studies ion migration in CuInP2S6 crystals using Raman spectroscopy. Ion migration is induced by applying an external electric field to the crystal, and the changes in the Raman spectrum are monitored in detail. Raman spectroscopic analysis revealed striking shifts and intensity changes in some vibrational modes, indicating the migration of copper (Cu) and indium (In) ions in the crystal lattice. The spectrum shows a splitting of the 320 cm−1 peak into two spectral components at an electric field strength of 600 V, which leads to the appearance of the 307 and 317 cm−1 peaks. Analysis of these spectral features and their dependence on the electric field strength provides an understanding of the dynamic behavior of ions in response to external influence. The results of this study further contribute to the experience of ion migration in CuInP2S6 crystals and to the fundamental understanding of ion transport in layered thiophosphates, leading to the design and development of improved materials for future technological applications.