In this study, we examine the hypothesis that preservice teachers' teaching motivations change during the first two years of their teacher preparation. A sample of 1,779 student teachers with two time points from Austria, Germany, and Switzerland is used. Findings show that student teachers' intrinsic motivation increases, whereas their extrinsic motivation being more distal to initial teacher education does not change. Against our expectations, their altruistic-type motivation (e.g., the motivation to work with children/adolescents) tends to deteriorate. The change of teaching motivations is influenced by in-school opportunities to learn (teaching practice activities, support by school mentors) and it is more practically relevant in a teacher education context where practical training is given high priority (Austria, Switzerland) compared with a context that heavily focuses on theoretical study (Germany). We discuss implications for teacher education from a comparative perspective and give an outlook for possible future research.