Background: Recent studies have provided evidence that marine algae sulfated polysaccharides and phlorotannins play an important role in human health. The aim of this study was to evaluate the anticoagulant activity of five marine algae extracts from Bejaia’s coast (Algeria). Methods: Phenolic and sugar contents of the five marine algae were assessed using folin ciocalteu and anthrone reagents, respectively. The anticoagulant activity was evaluated by the Activated Partial Thromboplastin Time (APTT) and Prothrombin Time (PT). Results: Higher contents of phenolic compounds were obtained with ethanol for Cystoseira humilis, Halopteris scoparia, Padina pavonica, and Rhodomela confervoides (8.55±0.29, 7.84±0.47, 6.41±0.14 and 4.16±0.04 mg CE/g of dw, respectively). Whereas, for Sargassum vulgare, the extraction with acetone showed higher content (3.04±0.071 mg CE/g of dw). The determination of sugar content showed that acetone extract of the five seaweeds was the richest in sugar, this rate increasingly dropped in ethanol extract and the fractions A and B. The red algae Rhodomela confervoides showed a significant anticoagulant activity in ethanol extract and the fractions A, B, and C, with elongation up to 407.97±58.12 s in the fraction C, at a concentration of 10 mg/mL. Anticoagulant activity was observed in the fractions A, B, and C of all the brown seaweeds. Procoagulant activity was observed in the fractions A and B of Cystoseira humilis and Sargassum vulgare, as well as the fraction B of Padina pavonica for an indeterminate period, at 10 mg/mL. Conclusion: The sulfated polysaccharides present in the fractions A, B and C of the studied marine algae may be responsible for the anticoagulant activity. So, they can be developed as a novel anticoagulant in the pharmaceutical industry.