The reaction of Ni(NO3)2·6H2O with the thio-modified nucleoside 2'-deoxy-6-thioguanosine (d-tG, C10H13N5O3S) in methanol in a 1:1.3 stoichiometric ratio deposited the title compound, [Ni(d-tG)3](NO3)2·2H2O, as green crystals. Despite the <1:3 Ni-ligand ratio used in the synthesis, the deoxy-thioguanosine binds to form three N7,S6-coordinated five-membered chelate rings with individual NiII ions in mononuclear complexes rather than bridge metal centres into more extended oligomeric or polymeric structures.