Purpose: Drawing on the perspectives of cultural capital theory, this study investigated the impact of international internships on the performance of Japanese undergraduates on the Test of English for International Communication (TOEIC) using a between-group pretest-posttest experimental design. Design/methodology/approach: Students participating in international internships were compared to their counterparts in a noninternational internship control group. Using TOEIC data collected in June 2019 and September 2019, we performed t-tests and estimated a difference-in-differences model with propensity score matching to measure the impacts of participation in international internships, students' demographic information, family socioeconomic status, and independent learning characteristics. Findings: The study showed that students' participation in international internships and independent learning activities had significant effects on TOEIC performance. The findings of this study also indicate that in addition to the effects of international internship experience and independent learning on students' English performance, learner learning behavior may be important for improving students' performance. Research limitations/implications: This empirical research provides meaningful insights for parents, educators, and researchers not only in Japan but also in a broader context in which international internships and independent learning activities have a crucial impact on student performance. It also sheds light on our understanding of the role of activities conceptualized through the lens of cultural capital in educational stratification. Originality/value: This study elucidates the association among cultural capital theory, international internships, and students' linguistic achievement and makes an important contribution to the broader conceptual literature.