Foeniculum vulgare Mill, known as fennel, is a medicinal plant of the Apiaceae family, widely used in traditional Algerian medicine. The aim of this study was to estimate the polyphenols and flavonoids content and to evaluate the antioxidant, the analgesic and the antiulcer activities of aqueous extract of F. vulgare seeds. Quantitative determination of total polyphenols and flavonoids revealed that this extract contained 551.45±0.010 mg gallic acid equivalent/g of dry extract and 284.83±0.008 mg quercetin equivalent/g of dry extract respectively. The study of the gastroprotective effect showed that this extract is able to protect the stomach against lesions induced by 70% ethanol. The percentages of protection were 55.54±6.99 and 71±3.09% for the 200 and 400 mg/kg doses respectively. The study of the analgesic activity indicated that the aqueous extract of F. vulgare reduced the pain induced by acetic acid (0.6%) with an inhibition rate of 47.89% and 68.65% for doses of 200 and 400 mg/kg respectively. Free radical 2,2-diphenyl-1-picrylhydrazyl and iron chelation tests were applied to evaluate the in vitro antioxidant activity. The free radical scavenging activity of F. vulgare extract against 2,2-diphenyl-1-picrylhydrazyl radicals revealed an IC50 value of IC50=30.91±0.49 mg/mL in comparison with gallic acid (0.038±0.0002 mg/mL). The iron chelating test showed that the extract had a high capacity for iron chelating, which was estimated at 0.346±0.003 mg/mL in comparison with the chelating reference agent, ethylene diaminetetraacetic acid.