The phosphorescence spectra from the three individual triplet spin sublevels of pyrazine‐d4 are obtained. The radiative rate constants are determined for individual vibronic bands of the individual sublevel phosphorescence spectra. Based on the radiative characteristics of the individual vibronic bands, the vibrational analysis is made anew. The assignments thus accomplished substantially differ from previously reported results. Anomalous behavior of the radiative rate constant ratios for the totally symmetric vibrations ν1 and ν9a is interpreted from the standpoint of the displacement of the potential energy surfaces. The nonradiative decay rate constants are found nearly identical to those of pyrazine‐h4 for any sublevels. The absence of the deuterium effect is discussed in relation to the nature of the accepting mode.