The EPR signalPbfrom interface SiIIIcenters in oxidized (111) and (100) silicon wafers has been observed to be enhanced up to 20 times under illumination with white light at liquid‐nitrogen temperature. The enhanced EPR signal saturates normally with microwave power, much like its unenhanced counterpart, which indicates that it is not a photoconductive pseudo‐EPR signal, as observed for other silicon surface defects. It is suggested that the effective spin polarization of SiIIIcenters is changed by the light. The optical effect, however, shows complications which may reflect coupling between thePbcenter and the semiconductor carriers.