Several 3-carbonyl (1–26), 3-acyl (27–52), and 3-carboxyhydrazido (53–58) coumarins have been synthesized in high yields (72–99%) and tested in vitro for their human monoamine oxidase A and B (hMAO-A and hMAO-B) inhibitory activity. Different substituents on the coumarin nucleus were evaluated for their effect on biological activity and isoform selectivity. Substitution at position C7 of the 3-ethyl