Valeriana ( Valeriana officinalis L.) is one of the oldest and most valuable medicinal plants in the world. Despite the long history of cultivation of this plant, the problem of weed control in this plant is not resolved. There is no selective herbicide for control of weeds of Valeriana yet. In addition, there have been no reports of salicylic acid (SA) effect alone or in combination with herbicides on Valeriana. So, this research was conducted to test the hypothesis that pretreatment with SA would enhance the ability of Valeriana plants to tolerate bentazon herbicide. The experiment was carried out as a factorial based on completely randomized design with three replications. Experimental treatments were three SA concentrations ( 0, 0.5 and 1 Mm ) and six level of bentazon herbicide (0, 0.50X, 0.75X, X , 1. 25X and 1.5X, X being equal to the recommended dose, 0.44 kg active ingredient ha -1 ). The Valeriana plant traits including herbicide phytotoxicity, the relative leaf water content (RWC), chlorophyll a, chlorophyll b, chlorophyll a+b, and total carotenoid contents, malondialdehyde (MDA) levels, antioxidant enzyme activities including ascorbate peroxidase (APX), catalase (CAT), guaiacol peroxidase (GPX), shoot and root dry weights, plant height and essential oil content were assessed. Single treatment of bentazon in recommended and increased dosage caused significant decreases in root and shoot dry weight, RWC, chlorophyll a+b and carotenoid concentrations and also increase in herbicide pytotoxicity, CAT, GPX enzyme activities and MDA content. When SA treated Valeriana plant were exposed to bentazon, all of the above mentioned plant traits were improved, suggesting that bentazon induced oxidative stress was diminished. SA pretreatment (0.5 Mm) had a strong effect on maintaining RWC, increasing of root dry matter, preventing chlorophyll and carotenoid degradation. Results of this experiment showed that exogenous application of salicylic acid can alleviate the toxic effects of herbicide in Valeriana. Amaranthus retroflexus behaved differently from Valeriana in that SA pretreatment along with bentazon application in recommended and higher doses had more efficiency in controlling this noxus weed specis. Keywords: Valeriana, oxidative stress, Bentazon, Salicylic acid, Amaranthus retroflexus