A series of metal complexes of Ni(II), and Cu(II) having the general composition [M(L)₂X₂] with thiosemicarbazide have been prepared and characterized by elemental chemical analysis, molar conductance, magnetic susceptibility measurements, mass, IR, electron paramagnetic resonance, and electronic spectral studies. The IR spectral data suggest the involvement of sulfur and terminal amino nitrogen in coordination to the central metal ion. On the basis of spectral studies, an octahedral geometry has been assigned for the Ni(II) complexes whereas tetragonal geometry for Cu(II) complexes. Thiosemicarbazide and its metal complexes have been tested in vitro against a number of microorganisms in order to assess their antimicrobial properties.