The vibrational spectra of ammonium sulfates found in nature are studied: tschermigite NH4Al(SO4)2(H2O)12, lonecreekite NH4Fe(SO4)2(H2O)12, ammoniovoltaite (NH4)2Fe2+ 5Fe3+ 3Al(SO4)12(H2O)18, sabieite NH4Fe(SO4)2, ammonioalunite NH4Al3(SO4)2(OH)6 and ammoniojarosite NH4Fe3(SO4)2(OH)6, to determine the behavior of ammonium in positions with inappropriate symmetry. The disordering of the ammonium cation in salt crystals was revealed, caused by the need to adjust the tetrahedral cation to the symmetry of the position in order to preserve the symmetry of the crystal. If the symmetry group of the position is not a subgroup of the symmetry group of the tetrahedron, the NH4+ tetrahedron is distorted by the subgroup Hʹ common for Td and H, where H is the symmetry group of the position. Then, a polyhedron corresponding to the symmetry of the position is constructed from N = |H|/|Hʹ| (|H|, |Hʹ| – the orders of these groups) distorted tetrahedra. The ammonium cation under disordering has several orientations (N), the superposition of which formally gives a polyhedron corresponding to local symmetry. For the given salts, the maximum common subgroups are C3ν and C3. The distortion of ammonium leads to activation of ν1, ν2 [NH4+] vibrations in the infrared spectrum and splitting of ν3, ν4 [NH4+] but in the case of finding the ammonium in a centrallysymmetrical position, as in ammonioalunite and ammonioarosite, the effect is hardly noticeable. On the contrary, in ammonium alum, ammoniovoltaite, sabeyite the band ν4 [NH4+] is noticeably split, and vibrations of ν1, ν2 [NH4+] are clearly seen in the spectra.