Purpose The aim of this study was to describe the distribution and composition of foraminiferal assemblages and granulometric properties of sediment in transitional environments along the eastern Adriatic coast. Another objective was to compare the results and establish correlations (similarities and differences) between these sensitive environments. Materials and methods Sediments from transitional environments were collected in December 2019 at three geographically separate sites: the Mirna salt marsh, the Soline mud plain, and the Nin intertidal plain. A total of 18 sediment samples (top 2 cm) were collected along the land-sea transect. Micropaleontological and granulometric analyses were performed. Identification of foraminiferal genera and species, absolute and relative abundance, and ecological (biodiversity) indices were determined on standardized samples. Particle size distribution was determined, which allowed classification of the sediment. Carbonate content and organic content analyses were performed as well. Results At the northernmost site, at the Mirna salt marsh, muddy sediments with low species diversity predominate. The Soline mud plain was characterized by greater species diversity and a uniform proportion of sandy and silty components in sediment. At the Nin intertidal plain, sediment was primarily sand with the greatest foraminiferal species diversity compared to the other two sites. The genus Ammonia dominated in all foraminiferal assemblages. Conclusions A different distribution pattern of benthic foraminifera in each environment was associated with variations in the grain size of sediment and was also influenced by the supply of freshwater from the river and karstic springs. Considering the lack of research on the transitional environments of the eastern Adriatic coast, this work provides more detailed data and emphasizes the importance of these environments and their biota.