To study the biological diversity of the Mollusca, six sites were selected along the perimeter of the Bahr AL-Najaf Depression, and samples were collected at a rate of three replicates monthly for the interval from November 2019 till January 2020. The results of this study showed that highest density of 224 individuals / 50 cm2 was recorded in January 2020. Eight species have been identified, 4 of which belong to Bivalvia: Corbicula fluminea, Pseudodontopsis euphraticus, Unio tigridis and Trachycardium lacunosum, 4 species belong to the gastropod: Melanopsis nodosa, Melanopsis costata, Melanoides tuberculata and Theodoxus jordani. Corbicula fluminea and Melanoides tuberculata were more abundant in study site compared with else species. The results of the constancy index showed that five species, one of theme belongs to Bivalvia and the rest belongs to Gastropod, where the other species were accessories to Bahr AL-Najaf Depression environment. The index values of Species richness varied between 2.5-6.5, while the Shanon-Weiner index ranged between 0.024-0.29 bit/ind., but the uniformity index ranged between 0.024-0.036.