Rhus coriaria L. (Anacardiaceae), also known as Sumac, is commonly used as a spice, flavoring agent, andas a traditional medicinal herb. This includes also the traditional use for treating asthma, catarrh, and common colds. Theaccumulating evidence supports its cardioprotective, antidiabetic, neuroprotective, anticancer, gastroprotective, antibacterial,anti-inflammatory, antiviral, antioxidant, and respiratory effects. However, there are no previous studies that have shown itseffects and mechanism in the airway smooth muscle tone, and therefore, the aim of our study was to investigate the in vitropharmacological action of R. coriaria L. extract (RCE) on the rat isolated tracheal and bronchial preparations by exploring itsrelaxant activity and mechanism of action. The direct relaxant effect of RCE (0.1–0.7 mg/mL) was tested in the rat bronchiand trachea rings precontracted by carbachol (CCh). In addition, the pretreatment with RCE (1 mg/mL) was tested on thebronchial and tracheal reactivity induced by CCh, potassium chloride (KCl), or CaCl2. In addition, the cyclooxygenaseinhibitor indomethacin and the nitric oxide synthase inhibitor N(G)-nitro-l-arginine methyl ester (L-NAME), respectively,were used for exploring the mechanisms of RCE-induced relaxation and reduction of reactivity. Our findings demonstratedthat RCE induced a concentration-dependent relaxation and a significant reduction of reactivity, significantly reduced witheither indomethacin or L-NAME. In addition, RCE decreased the responsiveness to KCl and affected the extracellular Ca2+-induced contraction in the tissues with added CCh or KCl in Ca2+-free Krebs–Henseleit solution. In summary, we have shownthat RCE displayed relaxant activities in the in vitro airway smooth muscles, and the possible mechanisms seems to involvethe prostaglandin, nitric oxide, and Ca2+ pathways. Taken together, our findings indicate the potential role of RCE in thetreatment of respiratory diseases with limited airflow, or obstructive respiratory diseases, and could justify its traditional use inthe respiratory diseases.