This thesis focuses on the role of parents for adolescents' development at career transitions within a framework of developmental regulation. In this framework, I assumed that adolescents' career-related activities are complemented by career-specific parental activities. Two main objectives guided my work: First, this thesis aimed at investigating the associations between career-related developmental regulation of adolescents and parents. Second, this thesis asked for the potential benefits of developmental regulation of both adolescents and parents. I integrated several lines of theory concerning adolescents' developmental regulation (referred to as self-regulation) as well as parents' regulation (referred to as other-regulation, Sameroff, 2010) to derive the research questions. Individuals face various career-related transitions during adolescence that channel their development in many ways (Nurmi, 2004; Salmela-Aro, 2009). These transitions take place within the educational system, e.g., a transition from one school form to another, or concern the entrance into the labor market, e.g., a transition from school to vocational training. Individual initiative is required to successfully master career transitions in adolescence (Nurmi, 2004; Heckhausen, Wrosch, & Schulz, 2010; Savickas, 2005). Previous theory and research on adolescents' developmental regulation have concentrated on what can be called phase-adequate engagement. Phase-adequate engagement encompasses behaviors which are undertaken by an adolescent to accomplish developmental goals related to an upcoming transition (e.g., Kracke & Heckhausen, 2008). Such goals can have different content, but have in common their focus on the transition. Appropriate developmental goals are thus in accordance with age-graded norms and standards (Nurmi, 2001; 2004). Previous research also demonstrated that phase-adequate engagement is benecial for adolescents. For instance, they are more likely to get an apprenticeship when they actively engage in writing applications (Nagy, Köller, & Heckhausen, 2005). Moreover, youths who are actively engaged are more satisfied with the choices they make (Schindler & Tomasik, 2010), and show higher positive affect after high school graduation (Haase, Heckhausen, & Köller, 2008) than those who are not engaged. Despite the importance of individual initiative for the successful mastery of career transitions, developmental psychologists have repeatedly stressed the fact that this initiative is embedded in a social context, i.e., the relationships with other people, and is bound to societal and institutional constraints (e.g., Silbereisen, Eyferth, & Rudinger, 1986; Vondracek, Lerner, & Schulenberg, 1986). In adolescence, parents are highly influential in youths' decisions about their future career (e.g., Youniss & Smollar, 1985). However, parents' role for adolescents' phase-adequate engagement has so far only been explored in a way that yields very broad conclusions. For example, there is increasing evidence which shows that having good relations to parents (in terms of, for example, a warm relationship and few conflicts) is correlated with several indicators of adolescents' career development (Whiston & Keller, 2004). However, theoretical conceptualizations of and empirical research on the actual processes through which parents influence adolescents are rather rare. The present thesis sets out to fill this gap. Since phase-adequate engagement comprises various behaviors, I focused on one aspect of it which has received a lot of attention in the literature: career exploration. Exploration encompasses the process of seeking and processing information, and of comparing alternatives, which informs an individual's choices about future career (e.g., Patton & Porfeli, 2007). With regard to parents' other-regulation in the domain of career, no systematic work has been carried out so far. I thus worked out a conceptualization and operationalization of parents' career-specific behaviors. I sought to answer five research questions with multiple studies and with data gathered in different ways. On the one hand, I collected data on two time levels: the macro-level (from year to year) and the micro-level of development (from week to week, cf. Lichtwarck-Aschoff, Kunnen, & van Geert, 2008). On the other hand, I gathered data from adolescents as well as from their mothers and fathers. I conducted five empirical studies, based on four different data sets to tackle the five research questions outlined below. Three data sets pertained the macro-level of development with adolescents facing high school graduation. Furthermore, I conducted a diary study with weekly assessments during the application process to university, which is a new approach in the domain of adolescent career development. The main results can be summarized as follows according to the five research questions. First, how do actual processes of phase-adequate engagement look like at the transition to college? This question was tackled on a week to week level. The results point to a lot of variability both between youths and within individuals. On the one hand, the results revealed inter-individual differences in how adolescents made a choice concerning their college major which corresponded with the amount of exploration they engaged in. On the other hand, the results showed that exploration is a highly fluctuating behavior which changed from week to week. Second, given the objective to study parental other-regulation, how is parental career-related involvement best to be conceptualized? I developed and validated a questionnaire instrument to capture parental other-regulation. This instrument comprised three facets of parents' career-specific involvement: support, interference, and lack of engagement. Third, how are adolescents' phase-adequate engagement and parents' involvement associated? Taken together, the results of the different studies conducted revealed that parents' support related positively to adolescents' exploration. Moreover, the role of interference was dependent on the type of exploration studied, and on the level of analysis (macro- vs. micro-level). Interference, and to some extent lack of engagement, were positively related to decision-problems in youths. Fourth, do the intensities of and the associations between adolescents' and parents' developmental regulation depend on temporal and process characteristics related to a transition? Empirical support was found for the assumption that adolescents' exploration would be affected by process features of a transition. Parents' involvement was adapted to the situation of the adolescent and was also affected by process characteristics. Fifth, what is the payoff of adolescents' phase-adequate engagement for process satisfaction while making the transition from school to college and for later adjustment to college? Are there such benefits of parents' career-related involvement as well? The results of the diary study showed that both youths' exploration and parents' support contributed to higher process satisfaction during the transition to college. Moreover, the results revealed that forming a strong commitment to one college major option, combined with higher levels of exploration, was associated with better adjustment later in college. In sum, the development of appropriate measures made it possible to test theoretical assumptions concerning adolescents' and parents' developmental regulation at the macro- and the micro-level of development. The empirical results further provide a basis for future research that focuses on possible mechanisms of self- and other-regulation. This thesis concludes with suggestions for future studies rooted in a dynamic view of development (van Geert & Steenbeck, 2005).