Medicinal plants are promising, as source of alternative solution to the problem of parasitic helminth infections that hamper the sustainable supply of products from farm animals. Ocimum gratissimum and Cymbopogon citratus leaves are commonly used internally to treat worms, relieve abdominal pains and stomach ache. This study, therefore, evaluated their leaf extracts for anthelmintic activity against Haemonchus placei worm from cattle; the most active extract being subjected to phytochemical analysis. The extracts, obtained by maceration using acetone, were evaluated for anthelmintic activity by exposing adult H. placei to a range of concentrations (5-60 mg/mL) for 3 hours and then counting the number of confirmed dead worms. Anthelmintic activity data were fitted to a non-linear regression equation (Log [extract] vs. response; variable slope) to produce best-fit sigmoidal curves from which LC50 values were computed. The best-fit LC50 values, found to be significantly different (alpha < 0.0001), were 17.70 mg/mL and 56.04 mg/mL for C. citratus and O. gratissimum, respectively, suggesting that C. citratus is three times more potent than O. gratissimum. Phytochemical analysis of C. citratus indicated the presence of alkaloids, tannins, steroids, saponins, terpenoids and flavonoids. Cymbopogon citratus could be useful as an anthelmintic phytomedicine against livestock parasitic helminths. Keywords: Anthelmintic; Haemonchus placei; Motility assay; Ocimum gratissimum; Cymbopogon citratus
