Abstract: Decoction of Detarium microcarpum, used by traditional herbalist as antidiarrheal agents, was investigated for its efficacy. Determination of phytochemical constituents of the aqueous extract was carried qualitatively using standard laboratory procedures. Experimentally-induced diarrhoea and intraluminal pooling and charcoal transit time using castor oil was used as a model for assessing antidiarrheal efficacy of the plant. The result showed that the plant contain alkaloid, tannins, flavonoids and carbohydrates. The extract gave a protection against castor oil induced diarrhoea of 53% compared with standard drug loperamide that gave 91% protection. Intraluminal fluid volume was significantly (p≤0.05) decreased compared negative control. Distance travelled by charcoal meal was found to be significantly (p≤0.05) lower than the negative control and is comparable to with the positive control group that received atropine. The results of this study suggest that the plant was found to possess antidiarrheal effect as claimed by herbalist.