Few studies have examined the impact of mastery learning on mastery goal structures or even on students' motivation more generally. In this study, we examined one middle school that implemented a schoolwide mastery learning system, conducting interviews with a sample of administrators (n = 3), teachers (n = 4), and students (n = 9) to determine how the system was envisioned by the school leadership, implemented by the teaching staff, and perceived by the students. We used deductive qualitative analysis (DQA) to determine visions, practices, and perceptions aligned with achievement goal theory. Results indicated that evaluation practices have the greatest potential to undermine other positive motivational impacts of mastery learning-based instruction. Implications and transferability for research and practice are discussed.