In plants, one of the most common modifications of secondary metabolites is methylation catalyzed by various methyltransferases. Recently, a new class of methyltransferases, the SABATH family of methyltransferases, was found to modify phytohormones and other small molecules. The SABATH methyltransferases share little sequence similarity with other well characterized methyltransferases. Arabidopsis has 24 members of the SABATH methyltransferase genes, and a subset of them has been shown to catalyze the formation of methyl esters with phytohormones and other small molecules. Physiological and genetic analyses show that methylation of phytohormones plays important roles in regulating various biological processes in plants, including stress responses, leaf development, and seed maturation/germination. In this review, we focus on phytohormone methylation by the SABATH family methyltransferases and the implication of these modifications in plant development.