Abstract Infrared and Raman spectra of four rare earth (Ho, Eu, Nd and Pr) double sulphates have been recorded and analysed based on the vibrations of methyl ammonium cations, sulphate anions and water molecules. Formation of hydrogen bonds of the type N H⋯O and O H⋯O are identified in all the compounds. Bifurcated hydrogen bonds are present in the compounds with dimethyl ammonium cations. The sulphate anions are distorted and occupy a lower site symmetry in the compounds. The bands obtained for (CH 3) 2NH 2 and SO 4 2− ions indicate that the structural bonding of (CH 3) 2NH 2Eu(SO 4) 2·H 2O and (CH 3) 2NH 2Ho(SO 4) 2·4H 2O is identical. Electronic transition bands of Eu 3+ and Nd 3+ observed in the Raman spectra of these two compounds have been identified and discussed.