This article reports a study that investigated Vietnamese doctoral students' motivations to pursue their doctoral study outside their home country. Analyses of in-depth interviews with 19 participants revealed what made a PhD abroad imaginable to them, thus revealing the motivational factors for Vietnamese doctoral students to sojourn for their academic undertakings, including professional requirement and academic development, life enrichment and self-exploration, prior transnational experiences and funding availability. Using the conceptual tools of imagination and capacity to aspire, the study highlights not only the capacity to navigate the horizons of aspirations of Vietnamese doctoral students but also the unevenness of imaginative spaces among them. Going beyond the push-pull framework or the traditional binary of external-internal motivation, this study, with a particular focus on imagination and aspiration, emphasises the capacity of the doctoral students and the socio-cultural context that made a PhD abroad a possibility for them. It further illuminates how their capacity to aspire was different from one another, leading to dissimilarities in their imaginative space and maps of horizons.