A simple and efficient methylthiolation protocol was successfully established for the synthesis of ketone-substituted indoles bearing 3-methylthioether moiety. The new synthetic approach featured metal-free oxidation and methylthiolation of alcohol-containing indoles, in which new C–S bond and CO bond were formed simultaneously using dimethyl sulfoxide as the sulfur source under the Swern oxidation conditions. The methylthiolation reaction provides a simple and facile procedure to methylthiolated indoles from readily available starting materials in good yields.