This study investigates potential herbicidal effects of Pennisetum purpureum extracts on two selected weed bioassay species. Ethyl acetate extract of P. purpureum was able to suppress germination of bioassay species by 41%. Although, it had no phytotoxic activity on the root or shoot growth of bioassay species, it had caused leaf discs of bioassay species to turn dark brown. Chromatographic separation of ethyl acetate extract yielded nine fractions. The highest suppressive ability was exhibited by fraction five where the shoot and root growth of bioassay species was inhibited markedly, while the colour of leaf discs changed from green to dark brown. The germination of the bioassay species is particularly sensitive to the fraction five, exhibiting approximately 20% reduction in germination, relative to the control. These results imply that P. purpureum contains phytotoxic compounds that can be developed as natural herbicide.Key words: Pennisetum purpureum extracts, allelochemicals, phytotoxic, bioassay.