Puffer fish, Arothron stellatus collected from Kasimedu fish landing station, Chennai was studied for its biological activity. Toxin was extracted from the skin of the fish using 0.1% acetic acid. The crude skin extract has shown inhibition activity against the bacterial and fungal strains. It has shown the maximum activity against E. coli and S. aureus and minimum activity against K. pneumoniae, antifungal activity was observed maximum against A. niger and A. flavus and minimum activity against T. viridae. Cytotoxicity of skin extract of fish was checked against HeLa cell line by MTT assay and the IC50 value were found to be 64.86 μg/ml. The results of the present study reveals puffer fish A. stellatus has bioactive compound which can be utilized for further development as drug.