Distribution of alien bivalves in the soft bottom of Iskenderun Bay according to physico-chemical parameters of sea water and sediment was investigated in this study, which was carried out in November 2005. A total of 2404 individuals belonging to 63 bivalve species were identified, of which 184 individuals belonged to 9 alien species. Alien species accounted for 14.3% of total number of bivalve species and 7.7% of total number of bivalve individuals. The most abundant species in the study area was the native species Anodontia fragilis (354 individuals). As for aliens, Afrocardium richardi was represented by a high number of individuals (155 individuals).