Significance The two-dimensional (2D) magnetic semiconductor CrI ₃ hosts a variety of strong and tunable magneto-optical effects and allows for the development of novel magneto-optical devices. While the elastic magneto-optical effects in CrI ₃ are well understood, its recently discovered inelastic magneto-Raman effect remains to have case-specific interpretations varying upon the thickness of CrI ₃ . We perform comprehensive Raman measurements on 2D CrI ₃ with polarization, temperature, layer number, and magnetic field dependence. We resolve a Davydov-split–induced N -fold multiplet in N -layer CrI ₃ and reveal the distinct magneto-Raman behaviors of individual phonons within the multiplet. Our results discover a layered-magnetism–coupled phonon scattering mechanism that explains the rich magneto-Raman effect in CrI ₃ of arbitrary thickness and elucidates the spin–phonon coupling physics in layered magnets.