Phytophthora infestans causes potato late blight. In this study, a strain of Serratia marcescens was isolated, and its volatile components were identified. Among them, 3-methoxytoluene exhibited strong antagonistic activity against Phytophthora infestans. The study investigated the changes in the proteome of Phytophthora infestans hyphae after 3-methoxytoluene (VOCs) treatment to elucidate the antagonistic mechanism.