Approximately 40-70%of crustaceans are caught, converted into waste that about 20-30%of shells of them is chitin. So, the shells of crustaceans are an appropriate source for chitin production. Chitosan is derived from chitin has a variety of biological activity. In this study, samples of blue swimming crab from Bandar Abbas coastal water were capturedin summer 2014. Chitin and chitosan from shells of crabs extracted using standard methods.The quantity and antimicrobial activity of chitin and chitosan extracted from different parts of crab Portunus segnis exoskeleton (carapace, claw, cephalothoraxesand walking legs) were examined against 11 bacterial and 3 fungal strains.Results showed that the amount of chitin and chitosan in the walking legs were significantly (P< 0.05) higher than other parts of exoskeleton. Chitosan showed slightly high antimicrobial activity than chitin extracted(P<0.05). Gram negative bacteria were sensitive to chitin and chitosan as well as gram positive bacteria.Bacterial strains showed more sensitivity than fungi against chitin and chitosan extracts. Carapace and claw shell chitosan was more effective than those from cephalothorax and walking legs. The range of MIC and MBC varied between 125-1000 μg/ml and 500-1000 μg/ml, respectively. According to the results obtained Persian Gulf shellfish was suitable for the chitin and chitosan production. Crustaceans of Persian Gulf can be used as a natural source for chitin and chitosan production. Also, better parts of crustacean shells for extract of these polymers can be identified. Effect of these compounds on some pathogens required further investigation.