This study investigated the phytochemical constituents and antispasmodic evaluation of crude methanolic stem-bark extract of Boswellia dalzielii. Phytochemical analysis revealed the presence of alkaloids, flavonoids, cardenolides, cyanogenic glycosides, higher fatty acids, saponins, tannins, steroids, cardiac glycosides, aloes, terpenoids and carbohydrates. The antispasmodic effect of the extract on isolated smooth muscle of the rabbit’s jejunum of acetylcholine (ACH) and barium chloride (BaCl₂) induced contractions have indicated a dose-dependent inhibition of the jejunal contraction from 18.9% to 79.4% and 34.1% to 84.2% with the bath concentration of (0.53-2.67 mg/ml) respectively. This study suggests that B. dalzielii extract interfered with the mechanism of jejunal rhythmic activity of the smooth muscle and hence could serve as good antidiarrhoeal and gastrointestinal remedy. The presence of tannins, saponins and flavonoids could be responsible for the remarkable antispasmodic activity observed from the study. This justifies the ethno-medicinal use of this plant as anti-diaarhoeal agent.