Lay Health Advisor (LHA) programs hold tremendous promise for reducing health disparities and addressing social determinants of health in medically underserved communities, including African American populations. Very little is understood about the capacity of LHAs in these roles and the broader contributions they make to their communities. This article seeks to address this gap by describing the characteristics and capacity of a sample of 76 female African American LHAs from a nationally disseminated evidence-based LHA program for breast and cervical cancer screening (The National Witness Project), as well as potential differences between cancer survivors and nonsurvivors who serve as LHAs. A conceptual model for understanding LHA capacity and contributions in underserved communities at the individual, social, and organizational levels is presented. We describe LHA experiences and characteristics (e.g., experiences of mistrust and discrimination, racial pride, sociodemographics), capacity at the individual level (e.g., psychological and physical health, health behaviors), capacity at the social level (e.g., social networks, social support), and capacity at the organizational level (e.g., role-related competencies, self-efficacy, leadership, role benefits/challenges). Data were obtained through interview-administered telephone surveys between 2010 and 2011. Findings highlight the critical capacity that LHAs bring to their communities and the importance of supporting LHAs to sustain these programs and to address racial/ethnic health disparities.