This article examines the history of ancestral tourism and its development as a form of cultural diplomacy between 1945 and 1966. The phenomenon often referred to as 'roots tourism' has during the last decades increased in popularity, especially in Old World countries that historically have sent large numbers of people to North America. While previous scholarship has focused on its existential dimensions and its relation to the twenty-first century tourism and heritage economies, this article looks at how ancestral tourism grew out of European attempts at expanding the tourism industry after 1945. It studies the international spread of 'person-to-person' programs that sought to turn travelers into 'ambassadors', and the subsequent transformation of such initiatives into 'homecoming' campaigns through notions of co-descent, targeting Americans of European descent. By exploring the case of the 1966 Homecoming Year campaign in Sweden, the article shows that the attraction of ancestral tourism was grounded in its ability to combine economic and political incentives articulated in the Marshall Plan. It developed out of a liberal-democratic ideology that vested individual travelers with diplomatic agency. In the process, European tourist agencies calcified the notion that ancestral tourism served not only individual experiences, but also national economies and international relations.