Electrochemical properties and third harmonic generation (THG) properties of bis(1,2-disubstituted-1,2-ethylenedithiolato) complexes were examined. This is the first time to report the THG properties of evaporated thin films of these complexes. Nonlinear optical (NLO) properties of these complexes in solutions were already reported by other research groups. It is notable that the title complexes show relatively large THG properties in both solid state and solution. It seems that the electronic state of these complexes by itself has some influences upon THG properties. The effects of the substituents in the dithiolato ligands were larger than those in the phenyl groups in the dithiolato ligands on both the reduction half-wave potentials and the THG properties. The reported molecular structure of bis(1,2-diphenyl-1,2-ethylene-dithiolato)nickel showed the planes of phenyl groups were not on the same plane as the metaladithiolene rings. These results suggest that the electronic state of the metaladithiolene ring have a large influence upon the THG property.