We contribute to research on social inequalities in educational attainment by examining the role of institutional contexts for students' study abroad (SA) intent and participation. To do so, we extend the individual-level rational choice model predicting SA intent and participation depending on students' socioeconomic status (SES) into a multi-level model emphasizing the importance of context effects. We test our model based on unique micro-level student data, which we supplement with context data. Examining 18,510 students nested in 69 universities, we provide the first in-depth multi-level analyses of SA intent and participation of students from Japan. In line with findings from many Western countries, our results show that higher-SES students are more likely to (intend to) study abroad. Regarding the role of institutional contexts, we find that programs designed to improve SA opportunity structures hardly affect students' SA intent but significantly positively affect SA participation above and beyond other university-level and student-level characteristics. Importantly, both lower- and higher-SES students benefit from favorable SA opportunity structures. These findings suggest that Japan's recent push toward internationalization of higher education has created relevant SA opportunities for students from different social backgrounds. Still, higher-SES students are currently overrepresented among those studying abroad because they are more likely to select into universities offering favorable SA opportunity structures. Our analysis calls for more research combining individual-level with contextual-level theories and data to better understand the conditions shaping SES-specific SA intent and participation.