AbstractGrowth of CdTe nanoparticles in glass is studied through the analysis of optical absorption spectroscopy with the help of a quantized state effective mass model. Glass includes nanoparticles with an initial size of ∼1.6 nm on cooling to room temperature from the melt at ∼1000 °C. Particles form by heterogeneous nucleation followed by diffusion‐limited growth. The narrowest particle size dispersion of 15% is obtained for an average radius of ∼2.28 nm at the end of heat treatment at 600 °C for 4.5 h. The magnitude of the absorption related to the number of particles is low due to the oxidation of Te. A combinative use of Arrhenius plots and the model yields an activation energy for diffusion of ∼170 kJ mol–1.