Abstract: Ethnomedically genus Origanum L. is commonly used in many countries due to its stimulating, analgesic, antitussive, expectorant, sedative, anti-inflammatory and antihelminthic agent. The aim of this research was to study the antioxidant potential of the aerial parts of origanum syriacum extract and to evaluate its effect on the modulation of restraint induced oxidative stress. Rats were treated with crude extract of origanum syriacum alone and both before (pre-extract stress treated) and after (post-extract stress treated) 6 h of stress exposure. Pro-oxidant effect of rat plasma was evaluated by determining the activities of Superoxide Dismutase (SOD), Catalase (CAT), Glutathione-S-Transferase (GST) and the levels of glucose, uric acid and lipid peroxidation (MDA). About 6 h of restraint stress caused a significant decrease in the activities of SOD, CAT and GST and the level of glucose, while increase in the levels of MDA and uric acid. The post treatment of crude extract was found more effective in restoring restraint stress induced changes in rat plasma than pre treatment. In order to reduce oxidative stress, observed in many pathological conditions, the O. syriacum extract can be given both as a prophylactic and therapeutic supplement for scavenging free radicals.