Electro- and magnetostriction mechanisms and temperature behavior of the length of bismuth-substituted neodymium iron garnet films on glass and gallium gadolinium garnet have been investigated. Electric- and magnetic-field and temperature dependences of the electro- and magnetostriction constants have been determined. It has been established that the magnetostriction constant changes its sign upon temperature variation. The experimental data are explained using a model of dipole glass with the magnetoelectric and magnetoelastic interaction.