Abstract: The marine invertebrates become one of hot spot for the lead of antimicrobial compounds. Two species of commercially available and edible bivalves (M. meretrix and M. casta) were assayed for antimicrobial activity against 10 bacterial pathogens and 6 fungal pathogens and its biochemical composition. The bivalves were extracted with three different solvent systems respectively methanol, ethanol and acetic acid. All the three extracts of both the species M. meretrix and M. casta showed highest antibacterial activities against S. aureus, E. coli, B. substillus, K. pneumonia, P. fleuroscence and V. cholera. In present investigation the methanolic extract of the two bivalve species of M. meretrix and M. casta was showed inhibition activities against all pathogenic fungal forms. The two bivalve extracts showed high amounts of protein content, which made the variation up to 160-180 μg mg-1 (wet weight). Both samples had low amount of carbohydrates 4.77-5.77 μg mg-1 and lipids 0.11-0.17 μg mg-1, respectively. The results of thin layer chromatography were revealed that presence of pink color spots it clearly indicates the presence of amino acid or peptides in bivalve’s samples. Presuming that the antimicrobial compounds were proteins or peptides. In SDS-PAGE on 12% gel, the crude proteins M. meretrix and M. casta showed 5-6 bands ranging from 45-223 kDa. They represent potential pharmacological leads perhaps possessing novel and uncharacterized mechanisms of action that might ultimately benefit the ongoing global search for clinically useful antimicrobial agents.