Subcritical water extraction (SWE) is a highly effective technique for extracting monoterpenes at elevated pressures and temperatures using only water solvent. This study investigated SWE of monoterpenes, including γ-terpinene, p-cymene, thymol, carvacrol, and thymoquinone, under varying extraction conditions of temperature (110–200 ℃) and time (5–20 min). The extract was qualitatively and quantitatively analyzed by gas chromatography. The maximal extraction conditions of p-cymene (0.11 ± 0.03 mg/g), thymol (0.40 ± 0.02 mg/g), carvacrol (5.28 ± 0.19 mg/g), and thymoquinone (1.28 ± 0.11 mg/g) were obtained at temperature/time of 150 °C/5 min, 200 °C/5 min, 200 °C/5 min, and 110 °C/5 min, respectively. Non-oxygenated monoterpenes, such as γ-terpinene and p-cymene, were either undetected or extracted in small quantities using SWE and were found to be more suited for organic solvent extraction. Oxygenated monoterpenes, such as thymol, carvacrol, and thymoquinone, exhibited optimal extraction when using SWE. By identifying the optimal conditions, SWE can be an efficient technique for selectively extracting target compounds from thyme. The selectivity of SWE could have practical applications in extracting desired compounds from a variety of industrials. SWE technology can be easily implemented on an industrial scale.