Metal-free methylation of a pyridine N-oxide C–H bond was developed using peroxide as a methyl reagent under neat conditions. Pyridine N-oxide derivatives with various groups (e.g., Cl, NO₂, and OCH₃) were all suitable substrates, and the desired products were obtained in moderate to excellent yields under standard conditions. Moreover, the methylation can be performed with a good yield on the gram-scale experiment. Tentative mechanistic studies show that the methylation is a classical radical process.