Valeriana wallichii D.C. (Valerianaceae) is widely used in folk medicine for the treatment of hypo-motility disorder of the gut. The aim of the present study was to scientifically rationalize its usefulness in the constipation. The V. wallichii leaves crude extract, which tested positive for the presence of anthraquinones, flavonoids, saponins, sterols, tannins and terpenes caused concentration-dependent (3-10 mg/mL) contractile effect in isolated guinea-pig ileum. Pretreatment of tissues with atropine (1 μM) completely abolished the stimulatory effect of V. wallichii leaves crude extract, similar to that of acetylcholine. These results indicate that the spasmogenic effect of V. wallichii is mediated possibly through the activation of muscarinic receptors, which provides sound mechanistic background for its medicinal use in constipation.