Methoxymethyl-2-pyridylsulfide (MOM-ON) is an effective methoxymethylating reagent when used in conjunction with AgOTf, NaOAc, and THF. A wide range of MOM ethers are produced from corresponding phenols and alcohols, including tertiary and allylic alcohols, in good yields and under mild, neutral conditions. This method is also effective for the methoxymethylation of avermectin aglycones.