The aim of this work was to valorize the microalgae Nannochloropsis gaditana grown in Algeria for the purpose of producing human and animal food supplements as well as bioactive substances. The microalga had a fresh matter content of 9.33±1.15%. The amount of ash (6.4 ± 0.23%) was high and reflected mineral richness. Total sugars represented 7.13±0.23%. Proteins and lipids represented 13.38±0.2% and 7±1%, respectively. The ethanolic (EENg) and methanolic (MENg) extracts obtained from 10 g of lyophilisates of N. gaditana represented respectively 24±1.65% and 14.2±0.7%. The evalu-ation of the polyphenols in these extracts showed interesting rates repre-senting 41.53±0.41 mg gallic acid equivalent (GAE)/g of EENg dry extract and 38.72±0.33 mg GAE/g for the MENg. The flavonoid contents were 19.82±1.65 and 18.61±1.45 mg quercetin equivalent (QE)/g respectively for the ethanol-ic and methanolic extracts of this microalgae. The condensed and hydrolyza-ble tannins represented respectively 0.35±0.04 and 0.63±0.09 mg of tannic acid/g of dry EENg. They also represented respectively 0.50±0.08 and 0.18±0.02 mg of tannic acid/g of dry MENg. The antioxidant activity generat-ed by the extracts EENg and MENg against 2,2-diphenyl-1-picrylhydrazil (DPPH ) and by the reducing power of iron (FRAP) seems appreciable com-pared to that of ascorbic acid. These results are in favor of the development of the microalgae sector constituting a futuristic vision to allow the development of the sector with a view to sustainability.