This study isolated the abietane diterpene ferruginol from the aerial parts of Fuerstia africana (Lamiaceae) collected near Ngong Hills, Kenya. It represents the first report of ferruginol in the genus Fuerstia. Antimalarial activity testing against the chloroquine-sensitive Plasmodium falciparum D6 clone showed strong activity with an IC50 of 1.95 mg/ml, while cytotoxicity against the human oral epidermoid cancer cell line KB was moderate with an ED50 of 8.1 mg/ml. Due to the correlation between strong antimalarial activity and cytotoxicity, ferruginol is not a desirable antimalarial candidate. Chemotaxonomically, the presence of ferruginol supports the close relationship between Fuerstia and Plectranthus (syn. Coleus) within the tribe Ocimeae of Lamiaceae, strengthens the chemotaxonomic relationship between Fuerstia and Salvia within the subfamily Nepetoideae, and further supports the placement of the genus Vitex (traditionally in Verbenaceae) into Lamiaceae.