The aim of this study was to highlight the importance of the hydro-soluble Opuntia ficus-indica L. seeds extract. To this end, various in vitro tests were performed to determine the levels of antioxidants (total polyphenols (TP), total flavonoids (TF), and condensed tannins (CT)) and to evaluate the antioxidant capacity (radical Diphenyl 1-Picrylhydrazyl scavenging activity (DPPH), ferric reducing antioxidant power (FRAP), Hydrogen peroxide scavenging activity (H2O2), and β-carotene bleaching scavenging activity (BB)) and anti-inflammatory activity. The results showed that O. ficus-indica seeds extract was rich in antioxidant compounds (TP, 905.71±42.50 mg GAE/100 g DW; TF, 50.77±0.08 mg QE/100 g DW; and CT, 98.99±8.19 mg CE/100 g DW). In addition, the seed extract exhibited high antioxidant capacity (DPPH, 248.40±1.06 mg GAE/100 g DW; FRAP, 382.56±1.70 mg GAE/100 g DW; H2O2, 62.01±0.57%; and BB, 83.87±1.76%) and high anti-inflammatory capacity. This study provides important insights into the presence of bioactive compounds and antioxidant capacity of hydro-soluble seed extract of O. ficus-indica.