Juniperus phoenicea is a tree of the Cupressaceae family that is popularly known in the south of Tunisia because of its wide application in herbal medicine, including the use of its leaves to treat many diseases such as diarrhea, rheumatism, and intestinal disorders. The aim of this study was to evaluate the ulceroprotective and antioxidant activity of essential oil extracted from the leaves of J. phoenicea (EOJp) against hydrogen chloride (HCl)/ethanol-induced ulcers in rats. The antiulcer activities of 50, 75 and 100 mg/kg body weight (b.w.) EOJp were investigated on 0.3 M HCl/ethanol-induced ulcers in rats. The essential oil yield was 0.69% with 48 compounds; α-pinene was the principal component (20.24%). In vivo pretreatment with EOJp given orally provided dose-dependent protection against HCl/ethanol-induced gastric ulcers in rats. Furthermore, pretreatment with EOJp significantly decreased malondialdehyde (MDA) content and increased the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx). The activity of the antiulcerogenic EOJp could be from synergistic antioxidant and anti-secretory effects. Oral use of EOJp has excellent preventive effects on induced gastric ulcers comparable to those of the proton pump inhibitor (PPI) omeprazole.