In enzymology, a caffeate O-methyltransferase (EC 2.1.1.68) is an enzyme that catalyzes the chemical reaction Thus, the two substrates of this enzyme are S-adenosyl methionine and 3,4-dihydroxy-trans-cinnamate (caffeic acid), whereas its two products are S-adenosylhomocysteine and 3-methoxy-4-hydroxy-trans-cinnamate (ferulic acid).

This enzyme belongs to the family of transferases, specifically those transferring one-carbon group methyltransferases.

The systematic name of this enzyme class is S-adenosyl-L-methionine:3,4-dihydroxy-trans-cinnamate 3-O-methyltransferase.

This enzyme participates in phenylpropanoid biosynthesis.

As of late 2007, two structures have been solved for this class of enzymes, with PDB accession codes 1KYW and 1KYZ.