The results of investigations the elastic and photoelastic properties of a number of garnets crystals obtained by Mandelshtam‐Brillouin technique including the data of ultrasonic experiments are represented. The velocity of sound propagation, the character of elastic interaction between ions in the lattice, nature of photon–phonon interaction in garnets is revealed. The mechanical, thermal and acoustooptical properties of garnets are rated using measured elastic and photoelastic data. The obtained results allow to predict a number of important characteristics of crystals with garnet structure and promote the development of materials with given properties.