Abstrac A huge volume of pollutant of industrial activities in Imam-Khomeini Port and Mahshahr Port discharge to water body of Khor-Mousa. Heavy metals cannot be decomposed, will be accumulated in organic matters, and might damage trophic chain. This study aims to determine the concentration of Heavy metals (Hg, Cd and Ni) in soft and hard tissue of the marine crab ( Macrophthalmus depressus , Rüppell 1830) and surface sediments of Khor-Mousa. Sediment samples were gathered from three sites with 12 marine crab of each site. Sample solutions prepared by drying and digesting samples using Aqua regia (mixture of hydrochloric acid and nitric acid with a 3:1 ratio). Then, using flame atomic absorption method the concentration of Cd and Ni was measured. For Hg concentration cold vapor atomic absorption technique with a mixture of sulfuric acid and nitric acid (ratio of 2:1) was used. Results showed that the average concentration of Ni, Hg and Cd in all sites was respectively 71.6, 6.3 and 3.8 µg/g for dry weight; 16.7, 6.2 and 3.3 µg/g for soft tissues; and 10.4, 2.9 and 3.5 µg/g for hard tissues. The concentration of Hg and Ni in sediments of the study area was higher than the sediment quality standards of the US EPA, and Cd concentration was closed to PEL standards. Results also revealed that the concentration of Hg, Cd and Ni in crab tissues was upper than WHO and FAO standards. Regarding petrochemical activities and related industries in Imam-Khomeini Port continuous monitoring of effluent wastewater is necessary. Keywords: Heavy metal pollution, Bioaccumulation, Crab, Khor-Mousa, Food chain.