The complexes [Ni{(RO)2PS2}2Tsc], [Ni{(RO)2PS2}2ApTsc], and [Ni{(RO) 2PS2}FurTsc.2H2O] where R = methyl (Me), ethyl (Et) or propyl (Prop); Tsc = thiosemicarbazide, ApTsc = 2-acetylpyridine- thiosemicarbazone, and FurTsc = furfuraldhydethiosemicarbazone have been synthesized and characterized by elemental analysis, conductance measurements, and spectral studies (IR, UV-Vis, and mass). Thermal studies of the complexes have been carried out using TG and DTG techniques. An octahedral structure has been proposed for all types of the complexes. A representative types of the complexes are tested against various pathogenic bacteria and fungi. The [Ni{(EtO)2PS2}2ApTsc] shows a high degree of activity against bacteria and fungi; this may be attributed to the pyridyl ring of the 2-acetylpyridinetluosemicarbazone ligand.