Abstract: This study investigated the sub-acute effects of aqueous root bark extract of Vitex doniana on some serum elemental components as well as serum biochemical parameters in rats. Serum sodium levels were significantly (p<0.05) increased following extract treatments while those of potassium were decreased. The extract decreased serum calcium concentration but no marked effect was observed on serum phosphorus concentration. The cholesterol level also decreased in the rats treated with higher concentration of extract (100 and 200 mg kg^-1), while the protein concentration in the serum of treated animals was comparable with that of control except at 200 mg kg^-1 which showed significant (p<0.05) decrease in protein level at 21 days of extract treatment. Levels of liver marker enzymes and blood urea nitrogen in the extract treated rats increased in a dose-dependent manner and could be due to the pathological lesions in the liver and kidney which are the main excretory system. The aqueous extract of Vitex doniana though used for the management of some illness such as diarrhea, jaundice, anemia, mental illness, rheumatism and as tranquilizer in man, has been observed in rats under the conditions of this study to be toxic to both the liver and kidney.