<p>This article examines the mission statements of U.S. nonprofit brands to investigate brand advocacy that bridges and binds internal and external stakeholders in the complex service ecosystem (e.g., U.S. healthcare). The empirics-first approach guides this investigation, which complements the theory-first, causality-seeking approach by using questionnaires and experiments to assess the pre-specified construct measurements and hypotheses. Using Structural Topic Modeling, this study shows how an empirics-first approach helps uncover nonprofit branding strategy practices with mission statements. Eight topic clusters emerged, indicating theory-consistent roles and anomaly-driven configurations under structural constraints. Four topic clusters align with Frumkin's institutional typology of nonprofit roles, but the other four clusters are disruption-driven anomalies—spanning epidemic advocacy, genetic disease, emergency medicine, and financial hardship—driven by service captivity and choicelessness grounded in undertheorized Transformative Service Research. The results reconceptualize mission statements as strategic vehicles for engaging various stakeholders and signaling positioning within multi-level service ecosystems. Implications for theory and practice are provided to enhance our understanding of branding strategies for navigating structural constraints, aligning stakeholders, and sustaining legitimacy across complex service ecosystems.</p>