**Published in Progress in Community Health Partnerships (PCHP) 17.3. All rights reserved.**
ABSTRACT Background: While sustainability is crucial to the success of community-based participatory research (CBPR) partnerships, there is a lack of conceptual clarity on what defines sustainability and what characterizes sustainability-promoting practices in long-standing (in existence > 6 years) CBPR partnerships. Objectives: The aim of this article is to explore the definition of sustainability, as well as practices that influence sustainability from the perspectives of academic and community experts in long-standing CBPR partnerships. Methods: This qualitative analysis is part of Measurement Approaches to Partnership Success (MAPS), a participatory mixed methods validity study that examined “success” and its contributing factors in long-standing CBPR partnerships. Thematic analysis of 21 semi-structured interviews was conducted, including 10 academic and 11 community experts of long-standing CBPR partnerships. Results: The key defining components of sustainability we identified include: distinguishing between sustaining the work of the partnership and ongoing relationships among partners; working towards a common goal over time; and enduring changes that impact the partnership. We further identified strengthening and capacity building practices at multiple levels of the partnership that served to promote the sustainability of the partnership’s work and of ongoing relationships among partners. Conclusions: Sustainability can be understood as supporting an ecosystem that surrounds the beneficial relationships between academic and community partners. Ongoing evaluation and application of practices that promote the sustainability of partnership activities and relationships may strengthen the long-term effectiveness of CBPR partnerships in advancing health equity.