We have detected an intermediate in the process of singlet-oxygen-sensitized delayed fluorescence (SOSDF) using tetra-tert-butylphthalocyanine (Pc) as the fluorescer and C-60 a'S the sensitizer. The observed intermediate is dependent on the concentrations of Pc, O-1(2), and O-3(2), as is SOSDF. By modeling the kinetics of the intermediate according to previously proposed mechanisms for SOSDF, we are able to rule out the singlet oxygen dimol as the intermediate. The intermediate kinetics are in agreement with either an exciplex or a triplet Pc mechanism. Since the intermediate has a spectrum identical to that of the triplet Pc, the triplet is the most likely intermediate.