The consolidation of regionalism as a broad field of research attracting scholars across disciplines demands an inquiry on its scientific foundations. This inquiry should consider the object of research, the methods and the theories used. First, regionalism scholars lack a consensually agreed definition of their subject. Second, research focusses mainly in case studies, led by area specialists and comparative research is a rather occasional methodological occurrence. Finally, regionalism has not produced significant theoretical advances vis-à-vis neighbouring disciplines. In summary, regionalism contribution to knowledge is scarce and this paper suggests, instead, applying mainstream political science and international relations objects, methods and theories.