4-Alkylthiopropylphenols were synthesized from corresponding 2,6-dialkylphenois via the allyl derivative. A comparative study of the antioxidant activity of the prepared compounds was carried out in five model systems. The rate constants for the reactions of the test compounds with cumene, styrene, and methyl oleate peroxide radicals were measured. It was shown that 4-thioalkylphenols with methyl and cyclohexyl ortho-substituents are powerful inhibitors in the oxidation of mineral oil.