Several aromatic plants have been experimentally cultivated and promoted in northern Thailand at the Royal Agricultural Stations; two of them are marjoram and sweet basil. Apart from supplying their fresh leaves for foods, they are also for essential oil production. However, there has been no report on the quality of the essential oils from these two plants cultivated in Thailand. This prompted us to investigate the quality of essential oils from marjoram and sweet basil cultivated in the highland area of Thailand. The overground parts of marjoram and sweet basil were collected from the Royal Agricultural Stations in Chiang Mai Province and subjected to hydrodistillation. The physicochemical parameters and chemical compositions of the hydrodistilled oils were determined and compared with those of the commercial ones. TLC and GC-MS were employed for the chemical analysis of the essential oils. The results demonstrated that their physicochemical properties (color, odor, specific gravity, refractive index, and solubility in ethanol) were not much different from the commercial ones. The GC-MS analysis revealed that the hydrodistilled marjoram oil contained 3- cyclohexen-1-ol (39.21%) as the principal component followed by -terpinene (9.00%) and trans-sabinene hydrate (1Risomer) (9.00%). Of the commercial oil, however, 1,8-cineole (57.16%) and linalool (17.88%) were major compounds. Linalool (60.03%) and eugenol (19.62%) were mainly present in the hydrodistilled sweet basil oil, whereas estragole accounted for 85.79% was dominant in the commercial oil. From this study, it was exhibited that both the hydrodistilled marjoram and sweet basil oils were different from the commercial ones in terms of chemical compositions. Consequently, factors leading to the variation in the amount of the chemical components in the marjoram and sweet basil oils are worth further investigating. The essential oil from sweet basil cultivated at the Royal Agricultural Station could serve as a rich source of linalool.