An efficient approach for the direct sulfanylation of 4-hydroxyquinolinones and 4-hydroxypyridones with aryl thiols in the presence of CuI/DMSO has been developed. The substrate scope is broad, allowing facile synthesis of a range of structurally diverse 3-sulfanyl-4-hydroxyquinolinones and 3-sulfanyl-4-hydroxypyridones in good efficiency.