The title compound, (C3H10N2)2[AlF6]F·3H2O, was obtained using the solvothermal method with aluminium hydroxide, HF and propane-1,3-di-amine as precursors in ethanol as solvent. The structure consists of isolated [AlF6](3-) octa-hedra, diprotonated propane-1,3-di-amine cations [(H2dap)(2+)], free fluoride ions and water mol-ecules of solvation. The Al-F bond lengths in the octa-hedral [AlF6](3-) anions range from 1.7690 (19) to 1.8130 (19) Å, with an average value of 1.794 Å. Each [AlF6](3-) anion is surrounded by three water mol-ecules and by six diprotonated amine cations. The 'free' fluoride ion is hydrogen bonded to four H atoms belonging to four dications and has a distorted tetra-hedral geometry. The three water mol-ecules are connected by hydrogen bonds, forming trimers that connect the AlF6 octa-hedra and dications into a three-dimensional framework.