Across three time-points spanning 9 months, changes in achievement goal orientations and contingencies of self-worth were assessed as a function of participating in a mastery-structured academic program for high-ability adolescents (N = 126). Endorsement of mastery goal orientations increased during the program and remained high even after students returned to their home learning environments. In contrast, performance-approach and performance-avoidance goal orientations decreased during the summer program, but returned to previous levels when assessed 6 months later. Latent growth curve models assessed the covariation of performance goal orientations and two contingencies of self-worth (outperforming others and others’ approval) hypothesized to represent elements of performance goal orientations. Changes in the contingency of self-worth based on outperforming others positively covaried with observed changes in both performance goal orientations; however, changes in self-worth contingent on others’ approval did not. Results are discussed in terms of mastery-structured environments’ potential to alter achievement goal orientations via their underlying psychological processes. Implications for achievement goal theory and the design of achievement-oriented environments are discussed.