Social and economic changes during the past decades have affected especially adolescents and young adults at the beginning of their working lives. In nearly all Western countries the school-to-work transition (STWT) nowadays is characterized by increased insecurity. The major aim of this dissertation thesis is to present the design and evaluation of a skills promoting training program for fostering a successful STWT in students on non-college bound school tracks. Based on the Life Skills approach, the school-based intervention program SCHuuuB targets variables that are considered as being relevant for actively and successfully mastering the STWT and later career development by current by current career theories and concepts. More specifically, it aims at promoting skills and resources related to career choice, implementing career goals, and social skills. The program consists of ten sessions (each 90 min) and is implemented by trained teachers provided with a structured manual. Program effectiveness was evaluated using a pre-posttest design with an intervention and a control group (N ≈ 600 ninth graders from 25 Thuringian non-college bound schools). Overall, implementation quality was good and the program was well accepted by teachers and students. Structural equation models specifying true intra-individual change showed positive program effects on different targeted variables. However, for the most part, these effects were dependent on students’ involvement in other career preparation measures implemented in schools. Specifically, effects were often evident only for students who did not take part in another Thuringian career preparation program with the primary aim of providing practical work experience. The results are discussed with respect to implications for the intervention program, career preparation during school time in general, and further basic research.