Fifteen seaweeds belonging to three classes of algae were analyzed for flavonoids. All the seaweeds studied were found as rich sources of flavonoids and it was varied from 6.03 to 33.39 mg/g. Differences among the flavonoids were apparent among the species. The Phaeophyceae members were observed with higher content of (with the range 20.72-32.89mg/g and mean of 26.80) flavonoids than the Chlorophyceae and Rhodophyceae. Among the fifteen species analyzed, Enteromorpha compressa(33.39mg/g) and Padina tetrastromatica(32.89mg/g) have higher content.