The influence of high-power ultrasonic treatment on the structure of amorphous iron(III) hydroxide xerogels prepared by precipitation from iron(III) nitrate solutions of different concentrations has been investigated. An analysis of the small-angle neutron scattering data allowed us to reveal for the first time that ultrasound substantially affects the mesostructure of amorphous xerogels, including the homogeneity, the fractal dimension, and the size of constituting monomer particles.