How do pre-service teachers perceive their own competencies in the different areas of their course of study? Why do they perceive their competencies like they do? The study at hand tries to answer these questions by qualitatively analysing the academic self-concepts (Marsh, 1986) of pre-service teachers in the field of didactics of technology and the influence of comparison processes (i.e. social ((Festinger, 1954), dimensional (Möller & Marsh, 2013), and temporal comparisons (Albert, 1977). For the first time, an interview study is being conducted to investigate self-concepts of pre-service vocational teachers and the associated ways of reasoning. The results show that especially social comparison significantly influences academic self-concepts and their development. Additionally, dimensional, and temporal comparisons also play an important yet subordinated role. The study at hand provides essential in-depth insights into the self-concept development of pre-service technology teachers thus offering opportunities of fostering their self-concepts and hence their future competencies.