From the analysis of 11 sediment samples collected between 45.1 and 100 m water depth in the Gulf of Pozzuoli (Tyrrhenian Sea), upper circalittoral benthic foraminiferal and ostracod assemblages were investigated to evaluate the relationships between meiofaunal composition, abundance, diversity, and sediment contamination derived from industrial and residential sources. The bay has been affected by significant chemical pollution for over a century, and high concentrations of contaminants are still preserved in the sediments, raising concerns for ecological and human health. Some species, such as the benthic foraminifer Nonionella turgida and the ostracod Cytheroma variabilis, show a positive correlation with geoaccumulation indices, suggesting a potential tolerance to elevated contaminant concentrations. However, both benthic foraminifera and ostracods display high abundance and diversity, indicating that these assemblages are supported by moderately productive and non-stressed environmental conditions. Nutrient inputs likely enhance primary productivity and food availability, while remaining below levels that would induce hypoxia or toxic effects.,Comparison between the circalittoral assemblages analysed in this study and previously investigated infralittoral assemblages allows a clearer definition of taxonomic distribution across the infralittoral–circalittoral transition, contributing to a better understanding of the ecological gradients characterising the Gulf of Pozzuoli. This transition is marked by the occurrence of taxa not recorded above 40 m water depth, including the benthic foraminifera Quinqueloculina viennensis and Q. padana, and the ostracods Bosquetina tarentina, Buntonia dertonensis, Henryhowella parthenopea, Krithe praetexta, and Rectobuntonia subulata, together with a marked increase in the abundance of the genus Cytheropteron, which is rare in the shallow waters of the gulf.