Narratives play a powerful role in sharing meaning and making sense of experiences. Specifically, health narratives convey storylines, characters, and messages about health-related behaviors and provide audiences with models for healthy behaviors, prompting audiences' health-related reflections and decision-making. Narrative engagement theory (NET) explains how personal narratives can be integrated into interventions to promote health. This study utilizes NET to test direct and indirect effects of teachers' narrative quality on adolescent outcomes during a school-based substance use prevention intervention that includes narrative pedagogy and an implementation strategy. Observational coding of teacher narratives in video-recorded lessons along with self-report student surveys (N = 1,683) were subjected to path analysis. Findings showed significant direct effects of narrative quality on student engagement, norms (i.e. personal, best-friend injunctive, and descriptive norms), and substance use behavior. The analysis also yielded support for indirect effects of narrative quality on adolescent substance use behavior via student engagement, personal norms, and descriptive norms. Findings highlight important issues related to teacher-student interaction during implementation and contributes implications for adolescent substance use prevention research.