The title compound, 4-ammonio-2,2,6,6-tetramethylpiperidinium chromate dihydrate, (C9H22N2)[CrO4]*2H2O, crystallizes in the monoclinic system with one organic cation and one chromate anion in the asymmetric unit, together with three independent sites for water molecules, two of which have their O atoms located on twofold axes. The structure is composed of layers built up from CrO4(2-) tetrahedra and water molecules alternating with C9H22N2(2+) cations and additional water molecules. Two types of hydrogen bonds, O-H...O and N-H...O, ensure the cohesion and stability of the structure.