The accumulation of macro litter along coastal beaches and dune systems poses a growing ecological threat. It harms biodiversity, endangers human health, and causes significant economic losses. In the Mediterranean basin, the increasing amount of waste washing ashore has become a major challenge, with waste management emerging as a critical environmental issue. This study analyses the accumulation patterns of coastal litter in the northwestern Adriatic and investigates its sources and composition to support targeted waste management actions. Litter was sampled at two Sites of Community Importance (SCI’s): SCI-IT5310006 “Fiorenzuola di Focara” and SCI-IT5310007 “Litorale Baia del Re” as well as at an unprotected beach, “Spiaggia Libera Sottomonte”. Using the standardized OSPAR protocol, data on litter abundance and composition were collected across 112 plots (2×2 m) distributed among the three sampling sites per season. Vegetation cover was also recorded to explore potential interactions between litter presence and dune plant communities. Preliminary results, based on Generalized Linear Models (GLMs), revealed significantly higher litter abundance within SCI sites, probably due to limited mechanical cleaning activities to avoid disturbing sensitive habitats such as protected dunes, compared to unprotected beaches where waste is regularly removed to allow activities for recreational purposes. Of the total debris recorded, 62.87% was plastic and 33.81% polystyrene, with approximately 40% likely associated with fishing activities originating from polystyrene boxes and plastic fishing nets. The high percentage of this type of litter is linked to its buoyancy and wind-driven transport over long distances. A strong positive correlation was found between plastic debris and proximity to urban areas (z = 26.85, p < 0.001), with fishing-related debris also significantly associated (z = 16.34, p < 0.05). This widespread pollution is driven by excessive plastic production and stronger enforcement and wider implementation of regulations to protect Mediterranean coastal ecosystems are required.