This study evaluated the concentrations of several heavy metals – lead (Pb), nickel (Ni), copper (Cu), zinc (Zn), cobalt (Co), cadmium (Cd), and iron (Fe) – in the tissues of the freshwater mussel Unio tigris collected from seven locations along the Tigris River in Maysan Governorate, southern Iraq. The analysis was performed using Inductively Coupled Plasma (ICP) spectroscopy. The results revealed significant variation in metal concentrations across the study area. Overall, high accumulations of the measured metals were observed in the mussels. The average concentrations in the mussel tissues decreased in the order: Fe > Co > Ni > Zn > Cu > Pb > Cd. Lower mean concentrations at certain sites appeared to correspond with fewer pollution sources in those regions, whereas higher mean concentrations at other sites (such as the Al-Eimarah stations) were associated with numerous pollution sources. The pollution levels in Unio tigris were further examined using the contamination factor (CF), enrichment factor (EF), geo-accumulation index (I-geo), and pollution load index (PLI). The findings from this research provide valuable baseline data on trace metal accumulation in mussel tissues, which can inform efforts to control potential poisoning from trace metal exposure and serve as reference information for assessing heavy metal pollution in aquatic ecosystems.