The strength of diasporic nationalism is characterised by an uneven historical geography, with different diasporic communities functioning as ‘hotbeds’ of nationalism at different times. Mapping and explaining these historical geographies is of importance if the cultural and political experiences of diasporic existence are to be understood. It is towards a critical interrogation of the conceptual tools available to accomplish this task that this paper is dedicated. Based upon a reading of social scientific literature on the intensity of national affiliation among the nineteenth and early twentieth century Irish diaspora, and using Doreen Massey's recent advocacy of a new concept of ‘space–time’, the paper advances a case for a (re)theorisation of the phenomenon of diasporic nationalism. In so doing, it is hoped that it will contribute to ongoing efforts to (re)theorise migration in four main ways: firstly, by identifying a subject area that provides a forum for population geography researchers to continue their growing dialogue with social and cultural geographers on the one hand and political geographers on the other; secondly, by reviewing the contribution of migration research to work in this area to date; thirdly, by offering a (re)theorisation of diasporic nationalism that places some traditional concerns of population geography at its core; and finally, by calling upon migration researchers to engage (once again) with contemporary debates within human geography about time and space, and to reflect upon how the conceptions of time and space which inhere within their work, condition the way they define and understand the settlement experiences of migrant groups.