Abstract: This study was conducted to assess the concentrations of cadmium and mercury in Najaf Sea at Najaf city through the accumulation of C and Hg in the soft tissue and in the shell for The benthic invertebrates which collected were: Bivalves: Corbiculla and Unio, Gastropods: Melanopsis and Bellamya. The samples were collected bimonthly from December 2016-October 2017 from four different select sites from Najaf Sea in Najaf city. The annual concentration of Cd in Corbiculla soft tissue was 0.094 μg/g while in the shell was 0.055 μg/g. While Hg concentration in soft tissue was 0.0341 μg/g while in the shell was 0.0069 μg/g. In Unio soft tissue the Cd concentration was 0.142 μg/g while in shell was 0.053 μg/g. Hg concentration in soft tissue was 0.057μg/g while in the shell was 0.021 μg/g. Melanopsis soft tissue had Cd concentration of 0.052 μg/g while the shell was 0.038 μg/g for Hg concentration in soft tissue was 0.0454 μg/g and in the shell was 0.0031μg/g. Bellamya was collected founding only in Spring and Autumn that the concentration of Cd in soft tissue was 0.087μg/g and in the shell was 0.051 μg/g while the concentration of Hg in the soft tissue was 0.038 μg/g and in the shell was 0.004 μg/g. The concentrations of Cd and Hg in all the collected benthos were found to be higher in Spring and Autumn than in Summer and Winter. Unio had the highest concentration of Hg among the collected benthos while Corbiculla had the highest Cd concentration. The soft tissues of bivalves and gastropods have higher concentrations of Cd and Hg than the concentration in the shell. In general the Cd concentrations in all collected organisms were higher than Hg concentrations.