A model for calculating the light scattering by a material during crystallization of phase-separated glasses is proposed. The crystallization of inhomogeneity regions (particles) formed as a result of liquid–liquid phase separation and distributed over the vitreous matrix is considered within the proposed model. It is shown that a maximum in the light scattering by the material can be observed when the degree of crystallinity is equal to 0.5–1. The maximum is caused by incoherent scattering that occurs in a mixture of amorphous and crystallized particles, and the conditions of its appearance are associated with the presence of the ordering elements in the mutual arrangement of particles. It is noted that these conditions are probably realized upon crystallization of sodium niobium silicate glasses.