Supplementary antioxidants are essential because of the innate production of reactive oxygen and nitrogen species through normal cellular metabolism. Phenolic compounds and flavonoids are known to be the principal antioxidant constituents of dietary and medicinal plants. As a widely used culinary and medicinal herb, Acmella oleracea was assessed for its antioxidant properties. Total flavonoid content was estimated based on the reaction between the plant extract and aluminium chloride. Total phenolic content was quantified using Folin-Ciocalteu reagent; and total antioxidant activity was determined by phosphomolybdate reaction. The total flavonoid evaluation showed that 1 g of the plant extract contains 28.7 mg of quercetin equivalent dry weight of the sample. In terms of phenolic content, 1 g of plant extract was estimated to contain 1.38 mg of gallic acid equivalent dry weight of the plant extract. The total antioxidant activity indicated that 1 g of plant extract contains 12.5 mg of ascorbic acid equivalent dry weight of the plant extract. These chemical estimations show that A. oleracea is a good source of antioxidants, and justify its medicinal and dietary uses.