<p><i>Juniperus sabina</i> is a dominant species in the desert and mountain ecosystems. There have been reports evaluating its chemical composition and biochemical values, however, investigation on its allelopathic effect which might facilitate its dominance&#xa0;remains largely unexplored, with the major responsible allelochemicals undetermined. In this study, we compared the allelopathic effects of the aqueous extract, ethanol extract, as well as the essential oil (EO) of <i>J. sabina</i> on seed germination and seedling growth of two receiver species, the dicot plant lettuce (<i>Lactuca sativa</i>) and the monocot plant ryegrass (<i>Lolium perenne</i>). Both the extracts and the EO exhibited significant allelopathic effects, with the EO showing the strongest inhibitory effect on the receiver plants: the IC₅₀ values of the EO, the aqueous extract and the ethanol extract on lettuce were 0.203, 2.544 and 8.142&#xa0;mg/mL, and 1.042, 4.802, and 4.898&#xa0;mg/mL on ryegrass, respectively; indeed, the EO completely inhibited seed germination of both tested species at a concentration of 4&#xa0;mg/mL. GC/MS analysis revealed that sabinene (40.1%) and cedrol (12.74%) were the most abundant constituents of the EO. Further bioassays simulating natural conditions confirmed that volatile organic compounds (VOCs) exerted significant inhibitory effects on seed germination and root length development of tested plants. Furthermore, the EO negatively impacted the cell division of <i>Allium sativum</i>, suggesting that it may disrupt the cell division process to suppress plant growth. Taken together, these results suggest that <i>J. Sabina</i> is capable of producing active volatile compounds with allelopathic activity to inhibit seedling growth of receiver species by interfering with the cell division process, which partly explains why it is a dominant species in the communities.</p> Graphical Abstract <p></p>