Violence is a critical health issue that compromises the strength of communities and permanently damages the lives of individuals and families. The impact of violence on health and well-being is particularly devastating in disadvantaged and minority communities, leading to negative health outcomes, including premature death. However, research suggests that communities can prevent violence and negative health outcomes by developing collective efficacy, which happens when neighbors share norms and values, trust one another, and are willing to intervene to address problems. Despite the importance of collective efficacy in preventing violence and improving health, almost no research has investigated actionable strategies to build collective efficacy in disadvantaged neighborhoods. This article describes a theoretical and conceptual model that illustrates how collective efficacy impacts community violence and related health outcomes. We begin by reviewing other approaches to community violence prevention, including criminal justice and developmental approaches. We then discuss how collective efficacy works and why it matters, including theoretical and empirical research explaining collective efficacy and its impact on community violence and health. We then discuss a research-based intervention that social workers can use to facilitate collective efficacy, including our conceptual model and the key components of the intervention. Finally, we discuss implications for social workers who are working with communities to address violence and related health issues.