The purpose of the study was to investigate the longitudinal reciprocal relationship between achievement goals and self-determined motivation of students transitioning from middle school to high school. Participants were 3343 students from 9th to 11th grade. The overall results showed that varying degrees of self-determined motivation from middle school (9th grade) influenced the adoption of achievement goals in the first year of high school (10th grade) and the pursuit of achievement goal in the 10th grade influenced subsequent degrees of self-determined motivation in the 11th grade. One of the notable findings is that while the initial pursuit of mastery-approach goals might begin with various degrees of self-determined motivation, involvement in the pursuit of mastery-approach goals strengthened autonomous motivation while weakening controlled motivation. The current study consolidates the theoretical and practical utility of mastery-approach goals in strengthening intrinsic motivation and internalizing external values.