Secondary-postsecondary partnership reforms have grown in scale and importance throughout the past few decades as part of the national agenda to increase college access, equity, and completion. However, little research has examined the role of the principal in cross-sector partnerships. This qualitative case study explores how one nationally acclaimed principal at an award-winning early college high school made sense of the cross-sector context and negotiated with K-12 and higher education stakeholders to maximize college opportunity for low-income, Latinx, and first-generation students. Our analysis integrates sensemaking and micropolitical theory to identify leadership practices that facilitate effective cross-sector collaboration, with implications for K-12 leadership and cross-sector partnership reform.