Alongside the educational expansion and internationalisation of economies, it has become more important for students' labour market success to spend part of their studies abroad. However, only a fraction of German students studies abroad. In particular, students from underprivileged families refrain from doing so. While the social selectivity of international student mobility is well documented, the mechanisms underlying this pattern of inequality are insufficiently understood. Aiming to narrow this research gap, we examine an early stage of the process leading to international mobility and address the question why students from underprivileged families intend to study abroad less often. Applying theories of rational choice and cultural reproduction, we develop a theoretical framework that integrates several mechanisms explaining the observed social inequality. Using a nationally representative panel data set from the German School Leavers Survey, we estimate logistic regressions and effect decompositions. Our findings indicate that underprivileged students' lower likelihood of forming a study abroad intention partially results from previous life course events. Related to their previous educational decisions and experiences, underprivileged students have worse performance-related preconditions for studying abroad. Furthermore, their higher cost sensitivity and lower benefit expectation explain their reluctance to study abroad.