Even though the concept has been introduced more than 2 decades ago, available evidence conventionally operationalises shared instructional leadership as a composite, which has missed the opportunity to reveal to what extent principal and teacher instructional leadership helps improve instructional outcomes. Using the complex survey data collected in China, this research employed a three-level structural equation model to investigate the multidimensional relationships among principal and teacher instructional leadership, teacher self-efficacy, and student learning outcomes. The results suggest principal instructional leadership is significantly related to teacher instructional leadership. Both are positively related to teacher self-efficacy and student performance, though the effect sizes vary noticeably. Using a survey design, this study has added international and nuanced evidence to the shared instructional leadership research, through an integrated model emphasising both principals' and teachers' leading roles.