A preliminary X-ray study of the title molecular salt, [Ni(CH4N2S)(6)](NO3)(2), has been reported twice previously, by Maar [Acta Cryst. (1961), 14, 894] and Rodriguez, Cubero, Vega, Morente & Vazquez [Acta Cryst. (1961), 14, 1101], using film methods. We confirm the previous studies, but to modern standards of precision and with all H atoms located. The central Ni atom (site symmetry (1) over bar) of the dication is octahedrally coordinated by six S-bound thiourea molecules. The crystal structure is stabilized by intra- and intermolecular N-H...S and N-H...O hydrogen bonds.