Vocational education and training (VET) programs are typically regarded as the means to enable successful school-to-work transitions. However, high rates of premature contract terminations in VET programs suggest that adolescents face difficulties during this transition. This paper aims to examine the determinants of persistence intention, claiming that persistence intention is a crucial indicator of imminent dropout decisions. The analysis is based on a longitudinal data set of trainees in dual VET programs in Switzerland (n = 1,163) containing two measurement points (before and after the transition from school to VET). Drawing on Social Cognitive Career Theory (Lent & Brown, 2008, 2013), we are interested in the effects of work adjustment indicators, selected characteristics of the vocational choice process, and environmental support before and after the transition on trainees' persistence intention. We use structural equation modeling to analyze both direct and indirect effects of different predictor variables on persistence intention. The results show significantly positive effects of both occupational self-efficacy and perceived person-vocation fit during the training program on trainees' persistence intention. Moreover, there are only indirect effects of anticipated person-vocation fit and occupational self-efficacy at the end of compulsory education. Trainees' relationship with the trainer also has an indirect effect on persistence intention. Social integration in the workplace is both directly and indirectly linked to persistence intention. Overall, the model explains 48% of the variance in persistence intention. Implications for VET programs and future research are discussed.