The aim of this work was to evaluate antibacterial, antifungal and antioxidant activities as well as alginate yield and quality of the brown seaweed Dictyopteris polypodioides, collected from the Moroccan Atlantic coast. The results showed that Dictyopteris polypodioides exhibited high activity against the most human pathogenic bacteria tested (Staphylococcus aureus, Bacillus cereus, Klebsiella pneumoniae, Pseudomonas aeruginosa, Escherichia coli, Enterococcus faecalis, Salmonella sp.). The species demonstrated also an important antifungal activity against both species of the pathogenic fungi Candida and the most tested phytopathogenic fungi (Verticillium dahlia, Fusarium oxysporum, Fusarium graminearum, Botrytis cinerea and Geotrichum sp.). The high total phenolic content (27.54±0.59 % dw) has been correlated with the important DPPH scavenging activity (84.13%) and the low EC50 (0.43mg/ml). Furthermore, sodium alginate yield was about 21.92 % dw considered within the range of those reported from other worldwide alginophytes used in the industry. Infrared spectroscopy analysis shows that the obtained spectrum exhibits strong similarities to the commercial sodium alginate, especially at the anomeric region of fingerprint (950-750 cm-1). 1H NMR spectroscopy demonstrated an alginate polymer dominated by guluronic acid (M/G = 0.7) and alternating blocks MG and GM (FMG = FGM = 0.41). In conclusion, Dictyopteris polypodioides seems to be a promising source of bioactive compounds and alginates in Morocco with controlled and ecologically sustainable harvesting.