Seabirds are vital, but overlooked, components of coastal marine ecosystems and may connect the marine and terrestrial environment at a global scale, significantly contributing to inter-habitat connectivity and the provision of multiple ecosystem services. Although the ecological and functional role of birds in terrestrial areas, islands in particular, has been deeply studied since the last century, the same does not hold true for coastal marine areas. Given the importance of coastal areas for seabirds worldwide and, at the same time, the high vulnerability of both, looking into the role of seabirds in influencing the ecosystem functioning in coastal areas is needed nowadays. Here, we review the current knowledge regarding the role of seabirds on coastal ecological processes giving particular emphasis on the linkage between the seabird functions that are crucial in influencing the ecological processes and the provision of ecosystem services, and disservices, for the human well-being. Seabirds can contribute to shaping coastal ecological processes and services in a multitude of ways, among which directly influencing trophic status, environmental contamination, biodiversity and food webs through trophic (bottom-up or top-down) and non-trophic processes. We identified areas for future research to further clarify this linkage and promote seabird conservation. Display omitted •Seabirds contribute to inter-habitat connectivity at global scale.•Seabird influence on coastal systems is overlooked compared to terrestrial systems.•Seabirds greatly influence ecological processes and functioning of recipient systems.•Seabird functions influence the provision of many ecosystem services.•More studies are needed to improve the knowledge in this field.