The present study investigated the impact of participation in Erasmus study abroad (SA) programmes on students’ self-efficacy in managing intercultural interactions. It employed a longitudinal design, in which 81 German university students who participated in student exchanges for one academic year (SA group 1) or one academic term (SA group 2), and 25 students who had applied for exchanges but continued studying at home (AH group) formed the abroad and comparison groups. Participants completed questionnaires at baseline/ pre-departure, after +3 and +9 months (SA group 1 only) abroad, and up to 9 months following their return. Results show significant gains in intercultural self-efficacy for students in both SA groups during the first 3 months abroad, but not during the remainder of longer stays (SA group 1). Levels of self-efficacy among students in the AH group tended to plateau during the entire study period. When measured at 9 months post-return, students’ levels of self-efficacy showed a tendency to decline. Thus, facilitating the development of self-efficacy in intercultural interactions would not only be important for students who do not participate in SA programmes, but also for enhancing sustainability of SA effects.