Technical Abstract: Evaluation of different tissues of A. annua for their nutritional contents and antioxidant potential demonstrated that the leaves and inflorescence had the highest percentage of protein, crude fat and in vitro digestible fractions but the lowest levels of detergent fibers. These tissues also had the highest composition of the major elements as well as manganese and copper. Their relatively high amino acid and vitamin profiles indicate a desirable nutritional balance adding to the high antioxidant capacities of leaves and inflorescences. Collectively, these high levels of the different nutritional constituents and antioxidant activity coupled with the negligible levels of inherent anti-nutritive factors, specially in leaves, establishes A. annua as a good reservoir of nutrients and antioxidants that might favour its use as a potential herbal tonic by humans or as an important supplementary feed additive for livestock production systems.