The crystal structure of the title compound, [Ni(NH2OH)6] SO4, has been determined at 298 K by photographic methods; the structure was solved by the heavy atom method and refined by block diagonal least-squares procedures to a residual of 0.095 (1166 independent reflections). Crystal data: triclinic, P1, a 14.026(3), b 6.741(2), c 6.358(1) Å, α-98.35(2), β 79.57(1), γ 95.06(2)°, Z 2. In the two crystallographically independent centrosymmetric cations, the nickel atoms are octahedrally coordinated by the ligand nitrogen atoms, <Ni-N>, 2.12 Å, <N-O>, 1.44 Å. The Ni-N-O angles range from 110 to 117°. The sulphate geometry is normal and undistorted.