Pure hydroxylammonium salts of fatty acids of 1 to 4 carbon atoms are prepared by reacting hydroxylammonium sulfate and alkali metal salts of fatty acids with 1 to 4 carbon atoms in solution at elevated temperatures and separating off the hydroxylammonium salts of fatty acids of 1 to 4 carbon atoms by(a) reacting hydroxylammonium sulfate and alkali metal salts of fatty acids of 1 to 4 carbon atoms in solution in water or alkanols of 1 to 3 carbon atoms or mixtures thereof at 20.degree.-70.degree. C.,(b) evaporating the solvent out of the reaction mixture to obtain a dry residue,(c) isolating the hydroxlammonium salts of fatty acids of 1 to 4 carbon atoms from the dry residue thus obtained by sublimation under reduced pressure.