There is increasing demand for theanine as a taste-enhancing additive and as a supplement for improving and maintaining human health. We describe the development of an ion-pair reversed-phase liquid chromatographic method for the analysis of theanine in tea. Samples may be directly analysed after sonication for 10min. The mobile phase consists of an aqueous 2mM solution of pentadecafluorooctanoic acid (ion pair reagent) and acetonitrile (82:18, v/v). The theanine peak is detected using a UV detector at 200nm. The limit of detection is 5.1ng and the limit of quantitation is 15.6ng. The method is accurate with recoveries higher than 97%.