The reactions of sulfilimines with TCNQ were undertaken to investigate the electronic structure of the sulfilimine. The reaction of ylide bond (S = N) of sulfilimine with the multiple bonds (C = C or C ≡ N of TCNQ does not occur, but new charge-transfer complexes were formed as products. The molar ratio of the sulfilimine and TCNQ in new charge-transfer complex I was 1:1.3. This ratio was determined by elemental analyses. The results of various thermal analyses indicated that these complexes do not have definite melting points. The reason for this result is that the sulfilimine is instabilized by the weakened ylide bond in the complex, because IR data showed that the electron transfer from ylide bond to TCNQ in the complex occurs and as a consequence, the bond strength of ylide bond is weakened. ESR measurements of various sulfilimine-TCNQ complexes were performed. It was also clarified from the measurements of conductivities that the behaviors of conductivity of new complexes are similar to those of typical charge-transfer complexes.