According to self-determination theory, students who learn English as a foreign language (EFL) can be motivated by autonomous or controlled reasons. These motivations change over time, and students could exhibit distinct motivational trajectories. However, previous studies have mostly adopted cross-sectional designs and overlooked the developmental aspects of motivation. Furthermore, there is little understanding of the key factors associated with students' distinct motivational trajectories. To address these gaps, we used parallel process growth mixture modeling to examine the trajectories of students' autonomous and controlled motivation. Participants were 467 students from four junior secondary schools who were surveyed over the course of a semester. Results revealed three distinct motivational trajectories: “increasing controlled motivation”, “stable motivation”, and “increasing autonomous motivation”. Students whose basic psychological needs were satisfied were more likely to be in the “increasing autonomous motivation” profile. Students across distinct profiles had varying levels of achievement with those in the “increasing autonomous motivation” profile showing the highest levels of achievement, and those in the “increasing controlled motivation” profile having the lowest achievement. This study underscores the significance of nurturing autonomous motivation and supporting students’ basic psychological needs in EFL contexts.