Seaweeds constitute an interesting source of nutraceuticals and phytochemicals with health protective effects. Hence the present study aimed at evaluating nutraceutical potenticals of the selected seaweeds(Ulva lactuca and Kappaphycus alvarezii) and to evaluate the sub-chronic toxicity of seaweeds.The seaweeds were analyzed for nutrients and nutraceutical potentials in terms of antioxidants,phytochemicals and antibacterial activity. The sub-chronic toxicity was tested in albino rats as per OECD guidelines.The parameters assessed included serum biochemistry, hematology, clinical symptoms, heavy metal toxicity in organs and histopathology of vital organs. Results revealed that the selected seaweeds were rich in nutrients and nutraceutical potentials.Serum hematology and biochemical parameters showed normal results. Histopathology examination revealed that the extract of U.lactuca showed mild abnormalities in histopathology in liver and kidney whereas K.alvarezii did not reveal any toxicological lesion and proved to be non toxic.It may be concluded that Kappaphycus alvarezii can be used safely by humans and further studies are needed to prove the mild toxicity of Ulva lactuca.