Abstract: Chromolaena odorata (L.) King and Robinson is a member of the Asteraceae family. Research shows that its diverse range of secondary metabolites contributes to its allelopathic properties but the phytotoxic potential of C. odorata from the Philippines has not yet been studied. Ethanol extracts of C. odorata leaves were tested on seed germination and seedling growth of Lycopersicum esculentum (tomato) in 7 and 14 days observation periods. The lowest concentration level of 0.5% ethanol leaf extracts significantly inhibited germination and seedling growth of L. esculentum in both observation periods. Column chromato graphic elution of ethanol extract yielded 11 fractions, each of which was subjected to bioassay. Only fractions 4 and 5 inhibited seed germination of L. esculentum at 25% concentration. Phytochemical screening of fractions 4 and 5 are positive for the presence of alkaloids and steroids which may have caused the inhibition of seed germination and seedling growth of L. esculentum.