Purpose: This study examines the deployment of excellent retired principals (ERPs) as system leaders to facilitate systemic professional capital building in Taipei City, Taiwan. It explores the unique approach of the Taipei City government and contributions of ERPs in driving educational reforms. Design/methodology/approach: This study combines the perspectives of system leadership and professional capital, and analyzes the roles and practices of ERPs in promoting professional capital in Taipei's local education system. It draws on qualitative data gathered through interviews and document analyses. Findings: The findings reveal that the Taipei City government adopted a systemic approach by appointing designated retired principals as system leaders. The findings are categorized into three themes. ERPs serve as systemic capacity-builders, enhancing leadership across the local education system; ERPs act as collaborators and bridge-builders, fostering joint work and a collective sense of professional responsibility; and ERPs function as facilitators and advisors, cultivating decisional capital by providing informed decision-making support based on their experiences and wisdom. These roles challenge the notion of late-career decline, highlight the ongoing contributions of ERPs to the education system, and extend professional capital beyond teacher development, influencing system-wide collective capacity-building, collective responsibility, and policy enactments. Originality/value: This study contributes to understanding how exceptional retired principals can drive systemic reform and build systemic professional capital. It expands previous research by highlighting the unique Chinese cultural context in Taipei City and continued contributions of retired principals to the education system.