Hammett σm and σp constants for PhTe and Te– substituents have been derived and compared with those of the Se homologues derived from the half-wave potential shift of the first reduction step of phenylchalcogenobenzophenone and the third reduction step of symmetrical bis(cyanophenyl) chalcogenide. For the PhTe, PhSe, Te–, and Se– substituents, the σm values are 0.20, 0.20, –0.57, and –0.59 and the σp values are 0.29, 0.22, –0.72, and –0.84, respectively. The σp value of the Te– group and all of the σm values have been determined for the first time.