Morphology of bivalves is determined by both genetic and environmental factors. The main objectives of this study were to establish whether the populations of mussel Mytilus galloprovincialis along the eastern coast of the Adriatic Sea differ in morphometric traits, and to examine which environmental factors influence the morphometric traits of these mussel populations. Data were collected for 1780 individuals sampled from 18 native and aquacultural populations. 13 morphometric traits were measured on mussel shells, and condition and gonadosomatic indices were also recorded. Bioclimatic data and physical and chemical properties of seawater data in Adriatic coastal zone were collected from several online environmental variables databases. It was determined that mussel populations along the eastern coast of the Adriatic Sea differ according to the morphometric traits, mostly by the position of posterior adductor muscle. Particular morphometric characteristics which would distinguish the populations according to the pollution status or geographical locations of sites were not found. High significant correlation between the seawater temperature and the shell volume, height, width and posterior retractor muscle position and width was found. Dissolved oxygen, organic carbon, chlorophyll and trace metals also showed correlations with some of the morphometric traits as well as condition and gonadosomatic indices, which indicates the influence of the environment on the mentioned morphometric traits.