The research aims at evaluating the chemical contents of methanolic leaf extract of Carissa edulis. The leaf of Carissa edulis was collected air-dried, ground to powder and extracted with methanol by cold extraction method to give a percentage yield of 28.03% ^w/_w. The antidiarrhoeal effect of the methanol leaf extract on castor oil-induced diarrhoea, intestinal charcoal meal transit and castor oil-induced enteropooling were determined. The leaf extract of Carissa edulis produced a significant dose dependent protection (p<0.05) against the castor oil-induced diarrhoea with the highest protection of 53.50% obtained at the highest dose tested (800mg/kg). The extract showed a significant intestinal charcoal meal transit (p<0.05) as it had 15.80%, 41.90%, and 50.30% inhibition respectively when compared to distilled water, the negative control (0% inhibition). Atropine however produced a significant increase (p<0.05) in intestinal charcoal meal transit at 76.50% inhibition. There were no significant differences (p>0.05) between the extract doses 200, 400, 800 mg/kg administered. The methanol extract at 200, 400, and 800 mg/kg showed 27.00%, 40.80% and 51.40% fluid accumulation respectively. The positive control loperamide (5 mg/kg) had 79.50% inhibition of intestinal content when compared to the negative control (distilled water treated rats) which had 0% inhibition. The results obtained from this study revealed that the leaf of Carissa edulis possesses antidiarrhoeal effect.