We contribute to research on social inequality in educational attainment by examining the role of institutional contexts for students’ study abroad (SA) intent and participation. We advance existing research in two ways. First, we better conceptualize social inequalities in SA choice by extending the usual individual-level rational choice models into a multi-level framework emphasizing the importance of context effects. Second, using unique micro-level data of students (N = 18,510, nested in 69 universities across Japan), which we supplemented with context data, we empirically examine how university-level opportunity structures shape inequalities in SA choice by students’ socioeconomic status (SES), thereby also providing the first in-depth multi-level analysis of SA in Japan. Our results show that good SA opportunity structures substantially promote SA intent and participation beyond other university-level and student-level characteristics. In fact, university contexts better explain social inequalities in SA intent and participation than student-level variables. Moreover, we find that lower- and higher-SES students equally benefit from good SA opportunity structures, but mid-SES students benefit the most. In summary, our findings indicate that Japan’s push towards internationalization of higher education created relevant SA opportunities – not only for students from well-off backgrounds, but also for the less affluent. These findings call for more research combining individual-level with contextual-level theories and measures to better understand the conditions under which individuals make decisions about SA.