Serotonin is a monoamine neurotransmitter that functions as a hormone, neuromodulator, and psychoactive agent. Peripheral serotonin is involved in lipid and glucose metabolism, and it may prevent the development of metabolic syndrome. Serotonin is biosynthesized from tryptophan and can be obtained from certain foods. However, information regarding the dietary intake of serotonin is scarce. In this study, we determined the levels of serotonin and its precursors, tryptophan and tryptamine, in 38 fruits and vegetables commonly consumed in Japan using HPLC-fluorescence detection. The highest serotonin levels were found in cherry tomato (12.44±0.19 μg/g of fresh weight), and the highest tryptophan and tryptamine levels were detected in potato and kiwi (64.47±1.54 and 6.38±1.24 μg/g of fresh weight, respectively). Thus, these foods may represent excellent dietary sources of serotonin and may be used to develop effective therapeutic strategies.