The present study examined whether students experience an increase in their general perceived self-efficacy through international academic mobility. Two hundred and twenty-one students at Leuphana University Lüneburg were enrolled in a test-retest study with two points of measurement including a time interval of approximately six months. Perceived self-efficacy was measured in a group of sojourners (n = 93), studying abroad for one semester, and nonsojourners (n = 128) who stayed at campus in Lüneburg. Sojourning was a significant predictor for participants' self-efficacy at the second measurement. In addition, the number of social contacts met with per week was discovered as a mediator for the development of higher self-efficacy abroad. Furthermore, high self-efficacy at the first point of measurement seems to prevent sojourners from perceiving a new culture as a threatening challenge. Lastly, selection effects of personality concerning participants' intention to study abroad were looked for, but not found. These findings help to understand the influence of studying abroad on students' perceived self-efficacy and provide further information about the possible causes of personality development.