Polychlorinated Biphenyls (PCBs) are mutagenic, carcinogenic, and persistent organic pollutants of the marine and coastal environment. No previous research has precisely used barnacles as potential PCBs bioindicators in the Caspian sea. The present survey was done to add the PCBs concentrations amongst the barnacle and sediment samples collected from 5 important Iranian ports besides the Caspian sea. Barnacle and sediment samples were collected from Astara, Anzali, Caspian, Kiashahr, and Chamkhaleh ports. Samples were transferred to the laboratory and analyzed for the presence and concentration of PCBs using GC-MS. Eighty different types of PCB were detected in the examined samples. PCBs concentration ranged from 02.00±00.10 to 53.00±00.60 ng/g. PCB-77 (53.00±00.60 ng/g in Chamkhaleh, 53.00±01.20 ng/g in Caspian, 53.00±02.40 ng/g in Anzali, and 53.00±2.7 ng/g in Astara ports) had the highest concentration in barnacle samples. PCB-52 (53.00±00.70 ng/g in Chamkhaleh port) had the highest concentration in sediment samples. PCB-114 had the lowest concentration amongst the barnacle (02.00±00.10 ng/g in Astara port) and sediment (03.00±00.20 ng/g in Anzali port) samples. This study is the first report evaluating the presence and concentration of PCBs in barnacle in the Caspian Sea. The role of barnacles and sediments as biomonitors of PCBs was determined. It seems necessary to set strict rules to prevent pollutants from entering the Caspian Sea.