The crystal structures of two double salts of ammonium nitrate (AN) and ammonium sulfate (AS) are reported. The double salts 2NH4NO3·(NH4)2SO4 (2AN·AS) and 3NH4NO3·(NH4)2SO4 (3AN·AS) show a very similar crystal structure packing with alternating layers of anions and cations. The solid-state ionic distribution is controlled by an extensive hydrogen-bonding network with ammonium groups as the donors and O atoms acting as the acceptors. Crystallographic studies were conducted at both room temperature (293 K) and 100 K. Increasing the temperature involves shortening the b axis in the case of the 3AN·AS salt. Quantification of fertilizer mixtures using the Rietveld method was also carried out by means of the structural models reported in this paper for both salts.