Distribution of polychlorinated biphenyl (PCB 101, PCB 153), Mercury (Hg) and methyl mercury (MMHg) in muscle, gill and hepatopancreas of blue swimming crab Portunus segnis from Persian Gulf were investigated. In addition, the relationships between crab size (carapace width) and PCBs, Hg, MMHg levels in tissues were investigated by linear regression analysis. There were significant differences in crab PCB 101, PCB 153, Hg and MMHg concentrations were detected between different tissues (ANOVA, P<0.05). The pollutants concentrations were highest in hepatopancreas whereas lowest in the muscle of all crab species. The recorded mean concentrations were 0.485 μg g−1 PCB 101, 1.89 μg g−1 PCB 0.463, 0.815 μg g−1 Hg and 0.471 μg g−1 MMHg. The results showed that significant relationships between PCB and Hg-MMHg levels and crab size were positive. Comparison between male and female indicated that the average PCBs and Hg-MMHg concentrations in tissues of male crab were found to be significantly higher than those found in the female crab.