Marine macrophytes are hypothesized to be a major temporary sink for microplastics. In this study, microplastic contamination was investigated in 15 macroalgal species and one seagrass from different sites in two lagoons of the northern Adriatic Sea: the Goro lagoon and the Venice lagoon. A high percentage (94%) of the macrophyte samples contained microplastics, ranging from 0.16 to 330 items g⁻¹ fw, with the prevalent size in the range 30–90 µm and an average contamination per unit of fresh weight of 14 items g⁻¹ fw. Microplastic contamination displayed a site-specific, rather than a species-specific, pattern of accumulation. In addition, exopolysaccharides (EPS) displayed a significant positive correlation with the microplastics ononcontamination on macrophytes acting as glue for the plastic particles available in the water column.