Background: Terminalia chebula Retz is traditionally used to relieve constipation. The current study was performed to investigate the pharmacological action of aqueous extract of Terminalia chebula seeds (ATC) in vitro and in vivo. Methods: Terminal pieces of rat ileum were suspended in organ bath containing Tyrode solution. The ileum spontaneous motility frequency and contractility were recorded isotonically. To induce ileal contraction, carbachol and ATC were added to the organ bath. In addition, the effect of hexamethonium, indomethacin, atropine, and verapamil on the ATC-induced ileal contractions was also investigated. The effectiveness of ATC on relieving morphine-induced constipation was investigated in an in vivo study by measuring the faecal number, faecal water content, and intestinal transit ratio. Results: ATC increased the frequency of ileum motility and tension of contraction dosedependently (P < 0.05). Responses induced by ATC were inhibited by pre-treatment of the tissue with verapamil. The ATC activities were not affected by atropine, hexamethonium, and indomethacin. The faecal number and faecal water content were increased dose-dependently by ATC (P < 0.05). Conclusion: The excitatory effects of ATC on ileal contractile frequency and tension are possibly mediated through Ca2+ channels activation. The results of the present study support the traditional usage of ATC for the treatment of constipation.