Background: School reforms requiring collaborations spanning multiple sectors are increasing in prevalence, but extant research has primarily focused only upon cross-sector partnerships involving education and social services. College and career readiness (CCR) reforms, such as the one highlighted in this study, are also often intrinsically cross-sectoral in nature. It is necessary to understand how such complex collaborations are developed and maintained. Purpose: This study examined how cross-sector collaboration has shaped the development and implementation of district-wide high school career academies in a large urban school district. Research Design: We applied case-study methodology to examine a mature cross-sector collaboration that guides and supports the district's career academy reforms. A meta-framework concerning cross-sector collaboration--developed by Bryson, Crosby, and Stone (2015)--supported our design, data collection, and analysis. Conclusions: Findings disclose a complex system of structures and processes to support reform implementation and illuminate the role and nature of cross-sector collaborations. This study provides an initial step toward understanding the elements, processes, and leadership required to develop and sustain cross-sector CCR reforms. The findings hold relevance for practitioners (e.g., how to develop and strengthen such complex reforms), community partners, and researchers (e.g., theory-building regarding reform-supporting elements and their interactions).