Nonanoic acid methyl ester is an esterified form of nonanoic acid. It is found as a volatile component following thermal oxidation of conjugated linoleic acid methyl ester but not linoleic acid methyl ester. It is cytotoxic to A549 lung carcinoma cells with an LC50 value of 104.09 µg/ml. Nonanoic acid methyl ester enhances the penetration of minoxidil into isolated hamster ventral ear skin when applied at a 10% concentration ex vivo. It is a substrate for the E. coli alkane hydroxylase system (AlkBGT), which oxidizes nonanoic acid methyl ester to produce 9-hydroxy methyl nonanoate, an ω-hydroxy fatty acid ester that can be used in the production of sustainable polymers.