Abstract : Ammoides pusilla of the Apiaceae family, an Algerian medicinal plant used in various countries to treat a wide range of disorders and diseases. The present study aims to determine the phytochemical profile and antioxidant activity, and to evaluate the acute toxicity of the aqueous extract of the aerial parts of A.pussila in Swiss albino mice. First, phytochemical screening and determination of polyphenols, flavonoids and catechic tannins in the aqueous extract of A. pusilla were carried out. Antioxidant activity by (DPPH and ABTS tests ; hydroxyl radical scavenging and β-carotene-linoleate bleaching assay) was assessed. The second part of our study is the acute toxicity experiment, three separate groups of mice (n = 4/group) received the aqueous extract of A. pusilla at single doses of 2 and 5 g/kg BW administered by gavage for 14 days. Body weight and relative organ weights were measured, and biochemical parameters were quantified. Phytochemical analysis revealed the extract to be enriched in flavonoids, catechins tannins, saponins, terpenoids and anthocyanins. Quantitative assessment revealed that the aqueous extract of A. pusilla was the richest in bioactive components, with total polyphenol, flavonoid and catechic tannin contents equal to 66.39 ± 0.06 mg GAE/g, 38.67 ± 0.01 mg QE/g and 0.01 ± 0.00 mg CE /g respectively. Results for antioxidant activity showed that aquoues extract exhibited the highest antioxidant activity, giving values of 87.27 ±0.98 % and 99.28 ± 0.20%, respectively, for DPPH and ABTS tests. In addition, the aqueous extract demonstrated strong activity in the OH- radical scavenging test (97.0%). The extract of A.pusilla showed notable inhibition of linoleic acid peroxidation (40%). The estimated acute toxicity (LD50) of A.pusilla aqueous extract administered orally to mice was greater than 5 g/kg BW. There was no change in body weight, relative organ weights showed a changes in liver and spleen weights, and the aqueous extract of A.pusilla did not induce changes in biochemical indicators (liver and kidney status), retaining a slight decrease in glycemia and cholesterol levels. The results indicate the potential of Ammoides pusilla as an important source of bioactive molecules for therapeutic applications against axidative stress. Our data indicate that acute administration of the aqueous extract ofA.pusilla is relatively non-toxic to male Swiss albino mice.