Heavy metals are major group of dangerous contaminants in marine environment. Due to their persistence, they may enter aquatic food chains and transfer from one trophic level to another. They also may be harmful for human being which is placed at the top of the food chain. Imam Khomeini’s Port is located in the north west end of Persian Gulf and ships traffic and several industries especially petrochemical industries around of the port, discharge various organic and non-organic contaminants such as heavy metals into this ecosystem. In this study in order to investigate the levels of heavy metals (Hg, Cd, Pb and Cu) in soft tissue of oyster Crassostrea gigas from Imam Khomeini port, oysters of the same size were sampled on March 2010 from 5 different locations including harbors of Petroshimi, Doc Sorsoreh, 15, 28 and 33 in the Imam Khomeini port. The samples were freeze dried and acid digested in order to determine their heavy metal content with atomic absorption spectrophotometry. Results indicated that the content of Hg, Cd, Pb and Cu in the oysters’ soft tissue were 3.12±2.97, 7.56±3.62, 7.1±3.30 and 440.57±66.17 µg/g of dry weight, respectively. The highest level of Hg, Pb and Cu were recorded in harbor of Petroshimi while the highest level of Cd was measured in harbor no 15.The concentration of Hg, Cd, Cu and Pb in bivalve soft tissue was more than standard limits. This can be dangerous for public health therefore regular monitoring of heavy metals in the area is recommended.