Both self-regulation and external regulation are key to understanding adolescents' learning and positive development at school. However, evidence on the joint development of self-regulated learning and externally regulated learning during adolescence is lacking. In addition, the current knowledge on interrelations between the development of adolescents' self-regulated learning, externally regulated learning, behaviors of teachers and parents in terms of autonomy support and achievement pressure, and academic achievement is very limited. The present multilevel longitudinal analysis focusing on the domain of mathematics (N = 1,542 German adolescents; annual assessments from Grades 5 to 9; mean age at Grade 5 = 11.79 years, SD = 0.71, 51.75% female) addressed these gaps. Results from multilevel latent basic growth curve models showed that self- and externally regulated learning decreased over the 5 years at both the individual student and the class level. Changes in self- and externally regulated learning were linked: Classes with higher levels of self-regulated learning at Grade 5 showed a stronger decrease in externally regulated learning over time. Initial levels of and changes in student-reported teacher and parental autonomy support and achievement pressure were associated with self- and externally regulated learning at the individual student level; student-reported teacher autonomy support and self-regulated learning were also linked at the class level. Self-regulated learning related positively to standardized achievement test scores but not to adolescents' grades. This study adds to the scarce evidence base on different regulatory forms of adolescents' learning and can inform future research on adolescents' positive development and educational practice.