Background: Research has shown that both achievement goal theory and self-determination theory (SDT) are quite useful in explaining student motivation and success in academic contexts. However, little is known about how the two theories relate to each other. Aim: The current research used SDT as a framework to understand why students enter classes with particular achievement goal profiles, and also, how those profiles may change over time. Sample: One hundred and eighty-four undergraduate preservice teachers in a required domain course agreed to participate in the study. Method: Data were collected at three time points during the semester, and both path modelling and multi-level longitudinal modelling techniques were used. Results: Path modelling techniques with 169 students, results indicated that students' autonomy and relatedness need satisfaction in life predict their initial self-determined class motivation, which in turn predicts initial mastery-approach and -avoidance goals. Multi-level longitudinal modelling with 108 students found that perceived teacher autonomy support buffered against the general decline in students' mastery-approach goals over the course of the semester. Conclusions: Data provide a promising integration of SDT and achievement goal theory, posing a host of potentially fruitful future research questions regarding goal adoption and trajectories.