This study assesses the potential impact of biogenic dimethylsulfide (DMS) emissions in the ocean on coastal urban pollutant concentrations along the southeast Pacific coast of South America. We simulated coupled photochemistry and transport of atmospheric pollutants using a dedicated WRF-SMOKE-CMAQ modeling system to compare two alternative scenarios, incorporating or excluding marine DMS emissions. The analyses focused on Quintero and Valdivia, located in central and south Chile, respectively. DMS sea-air fluxes during summer days predicted emission peaks in Quintero reached 3 µmol m-2 d-1 and 15 µmol m-2 d-1 in Valdivia. Most notably, the inland transport of marine air masses within the Quintero domain increased predicted SO2 by up to 18.5% in Chile’s capital (Santiago), located ~100 km inland, while producing spatially increase mean SO2 concentrations in Valdivia by as much as 7.4%. During summer days, the contribution from oceanic DMS to the SO2 budget was higher in the coastal region of Quintero (0.15–0.20 ppb) than in Valdivia (0.01-0.02 ppb), due to the high levels of hydroxyl (OH) and nitrate (NO3) radicals in the local atmosphere. However, in the maritime air of Valdivia, oceanic DMS was the primary natural sulfur source for SO2, contributing up to 0.06 ppb (a 200% relative change). Our results highlight the role of marine biogenic sulfur emissions in modulating regional sulfur chemistry in the southeastern Pacific coast and emphasize the need to include oceanic DMS emissions and chemistry in regional air-quality evaluations for Chile.