In the context of ongoing socio-political transformations, higher education is increasingly expected to foster open-mindedness and intercultural competencies among students. International mobility—before, during, or after graduation—has long been regarded as a key mechanism in achieving these goals. Programs such as ERASMUS are emblematic of this ambition within the European higher education area. Yet, despite strong institutional frameworks, participation remains uneven and underutilized. The factors shaping students’ decisions to engage in international mobility after graduation are manifold and not fully understood by research and educational institutions.

This research addresses this gap by exploring the interplay of individual, institutional, and social influences on the decision to pursue international mobility as career path. We conducted a qualitative study at the University of Strasbourg, focusing on alumni from two faculties: Economics & Management and Sports Science. A total of 28 semi-structured interviews were conducted with graduates who had completed Master's degrees and had undertaken professional mobility abroad for at least six months after graduation.

Our comparative analysis investigates the motivations and trajectories behind these graduates' geographic and professional mobility. Specifically, we examine the role of socialization processes, individual dispositions, life events, and the activation of social networks—both strong and weak ties—in shaping their mobility paths.

Two key findings emerge. First, contrary to common assumptions, our results indicate that the decisive factor in facilitating international mobility is not the students’ socioeconomic or cultural capital, but rather the relational capital they accumulate. Importantly, it is the weak ties—casual encounters, informal discussions, and spontaneous opportunities—that serve as decisive triggers for mobility decisions. These links, while peripheral to students' core networks, function as critical gateways to international opportunities.

Second, our study confirms the positive impact of early international experiences on subsequent career development. However, it also highlights a significant unintended consequence: many alumni do not return to their home country, citing better working and living conditions abroad. This ‘non-return’ raises critical questions about the broader implications of international mobility for national labor markets and higher education systems.

For universities and policymakers, these insights are crucial. Our findings suggest that existing institutional mechanisms fail to adequately account for the informal and relational nature of how international mobility is initiated. As a result, such opportunities at a university level remain unevenly distributed. Our work contributes to a rethinking of international mobility policies—not merely in terms of formal incentives, but by embedding conditions that foster informal, serendipitous exchanges within educational ecosystems.

Moreover, we provide recommendations to support higher education to reflect on its role in retaining talents. If international mobility implies the risk of a one-way brain drain, the long-term benefits for the home country diminish. Thus, we see opportunities for higher education to take a leading role in not only supporting students in going abroad, but also in creating attractive reintegration pathways for expatriates that encourage return and knowledge transfer.

Keywords: Mobility, Social Networks, Weak Ties, International.