Instructional quality is a hot topic in education. Among the possible factors that can influence instructional quality, distributed leadership has emerged as a particularly influential factor at the school level. This study argues that distributed leadership relies on teachers taking autonomous responsibility and engaging in innovative practices. However, few studies have investigated the impact of distributed leadership on instructional quality through teacher autonomy or innovativeness. As such, we developed and tested a multilevel mediation model to examine teacher autonomy and teacher innovativeness as mediators in the relationship between distributed leadership and instructional quality. We used hierarchical linear modeling to analyze data from the 2018 Teaching and Learning International Survey, which includes responses from 2451 senior high school teachers in Taiwan. The results indicate that distributed leadership negatively affected instructional quality but positively influenced teacher autonomy and teacher innovativeness. Teacher autonomy and teacher innovativeness directly contribute to instructional quality, acting as competitive partial mediators in the relationship between distributed leadership and instructional quality. This study's findings provide evidence for understanding the association between distributed leadership and instructional quality at the high school level in Taiwan. Moreover, this study suggests that teachers' autonomy and innovativeness effectively enhance instructional quality.