A new tris(ethylenediamine)nickel(II) complex [Ni(en)3]GeS2(OH)2·H2O containing a zero-dimensional thiohydroxogermanate [GeS2(OH)2]2− anion was synthesized using a solvothermal reaction. The compound crystallizes in monoclinic space group P21/n with cell parameters a = 8.676(3) Å, b = 13.574(4) Å, c = 13.976(4) Å and β = 92.67(2)°. The ethylenediamine (en) ligands are bidentate to the Ni2+ through the N atoms of the amine group resulting in a distorted octahedral environment around the transition metal. The solid-state 1H NMR shows four broad singlets attributed to the –CH2 and –NH2 protons of the (en) in addition to H2O and –OH protons. The EPR results indicate that the octahedrally coordinated Ni2+ cations are paramagnetic with two unpaired electrons. In agreement with the EPR results, the ZFC/FC magnetization measurements show a paramagnetic response. The title compound is a wide bandgap semiconductor (3.9 eV) and exhibits photoluminescence emission at 488 nm upon excitation (325 nm).