Abstract: In this study, the chemical composition of the essential oils isolated from leaves of Juniperus oxycedrus L. subsp. macrocarpa were analyzed and their phytotoxic effects were evaluated. All together, 41 compounds were identified, accounting for 96% of the total oil. The monoterpenes fraction amounted to 61% of the oil and was characterized by a high proportion of monoterpene hydrocarbons (55%), amongst which the most abundant was α-pinene (42%) and sesquiterpenoids (29%). Regarding the herbicidal activity, the oil completely inhibited seed germination and seedling growth of three common weeds: Phalaris paradoxa, Trifolium campestre and Lolium rigidum and the activity by direct contact was more effective than by fumigation. The findings of the present study suggest a possible use of these essential oils as natural herbicides.