Plastic pollution poses a growing threat to benthic ecosystems in coastal waters, yet assessments often emphasize surface accumulation while overlooking seasonal variability and seafloor impacts. This study evaluates the spatial and seasonal variability of plastic pollution levels in benthic ecosystems of the Bali Strait, a monsoon influenced region characterized by intense human activities and ecologically valuable habitats. A hydrodynamic model coupled with Lagrangian particle tracking was used to simulate surface plastic transport under Southeast and Northwest Monsoon conditions and to identify potential accumulation zones based on residence time patterns. The Pollution Load Index was subsequently applied to quantify relative plastic pollution levels across benthic habitats, including coral reefs and seagrass meadows. Model validation against tidal elevations, surface currents, and drifter trajectories indicates satisfactory performance for seasonal circulation and transport analyses. Results reveal pronounced monsoon driven contrasts in plastic pollution levels on the seafloor. During the Southeast Monsoon, high to extreme pollution levels are concentrated along the western side of the Bali Strait, particularly in the Alas Purwo and Bama areas. In contrast, during the Northwest Monsoon, elevated pollution risk shifts toward the western and southern coasts of Bali, especially along Kuta Beach, while most locations along the East Java coast remain at low pollution levels. These patterns reflect the combined influence of seasonal current reversals, coastal orientation, and shoreline morphology on plastic retention and deposition. Overall, this study demonstrates that benthic plastic pollution in the Bali Strait is highly dynamic and seasonally controlled. Integrating hydrodynamic driven accumulation estimates with the Pollution Load Index provides an operational framework for identifying seasonally vulnerable benthic habitats and supports adaptive monitoring and management strategies in monsoon-dominated coastal regions.