Introduction: Community coalitions with public health-related missions are formal, semi-permanent, action-oriented partnerships comprised of community members, representatives of government agencies, policymakers, and academic partners. Despite their potential to promote sustainable change, coalitions have had mixed success in effecting long-term improvements in community health. There is a need to assist them in developing strategies for improving and sustaining their functionality. The purpose of this study was to improve understanding of the elements of coalition success and sustainability that are vital to health-related community-based participatory research. Methods: Although the literature describes coalition functions for effecting sustainable programs and policies, most research reports on individual programs only, rather than looking at the breadth of community coalitions and the commonalities that contribute to their effectiveness. Semi-structured interviews (N = 42) with academic and community partners followed by a grounded theory analysis of the data address this gap and provide theoretical underpinnings of factors sustaining coalition effectiveness. Results: Seven domains emerged: (1) Characteristics related to coalition structure and processes; (2) Partner characteristics, e.g., diversity, patience, flexibility, expertise; (3) Community characteristics, e.g., capacity, ownership; (4) Partnership dynamics and synergy; (5) Tangible benefits; (6) Available resources, and; (7) Project characteristics. In all, 70 elements representing these categories influenced coalition effectiveness over time. Discussion: Sustained effectiveness means continual improvement, ongoing development of skills and structures to support positive change, and expanded program or policy activities that benefit stakeholders. Whereas community researchers have yet to reach consensus on the universal elements of sustainability, this study expands knowledge of the factors contributing to coalition effectiveness beyond initial project implementation.