2-(Phenylthio)phenols were successfully synthesized from simple phenols and aromatic halides by using dimethyl sulfoxide as the oxidant. The transformation was accomplished via tandem copper(I)-catalyzed C-S coupling/C-H functionalization employing the Cul/L [L = (E)-3-(dimethylamino)-1-(2-hydroxyphenyl)prop-2-en-1-one] catalyst system. The mechanism of the reaction was elucidated based on an isotope labeling strategy.