Diaspora, variously defined, denotes difference within a host nation and connection with a real or imaginary homeland elsewhere. Diaspora claims, that is, a location that entangles the national, otherness within the national (often construed as ethnic), and places across national borders, all this in vastly complex ways. The study of diaspora therefore requires an analogous scholarly location that brings into conversation national, ethnic, and area studies. The analysis of the U.S. "Greek diaspora," for instance, calls for cross-fertilization between American ethnic, Greek American, and modern Greek studies. This kind of systematic exchange did not materialize in the context of post 1960s U.S. academy, despite vocal calls for such dialogue. Here I demonstrate that "diaspora" was not a primary organizing reference for research in either U.S. Greek American or U.S. modern Greek studies, a lapse all too conspicuous if one takes into account the political, economic, and cultural importance of the Greek diaspora. Instead, dominant threads within Greek American and modern Greek studies developed along the trajectory of a nation-centric paradigm respectively, the former privileging the study of ethnicity in a national (American) context, the latter attaching analytical priority to Greece. As a result of this bifurcation "diaspora" was relegated to the margins, remained under-theorized, and was often neglected as a research prospect. From the perspective of Greek American studies and focusing on selective Greek American histories, texts, and institutional contexts, it is possible to illuminate the ideological underpinnings for turning diaspora into a contested terrain for both Greek American and modern Greek studies. Thus, the clashing positions can be charted against the ongoing transnationalization of Greek worlds as well as of the transnational turn in the humanities and social sciences, a parallel development that invites a fundamental remapping of Greek America and consequently obliges scholars of both Greek American and modern Greek studies to rethink their spatial and cultural frames of analysis. The operation of transnational geographies associated with Greek worlds calls attention to the artificiality of the boundary between Greek American and modern Greek studies and the necessity for joining their forces for the purpose of new critical mappings, a project now under way within U.S. modern Greek studies programs.