<p>This umbrella systematic review synthesizes existing conceptual approaches to sustainability across human, animal, and environmental health disciplines, framed within the One Health paradigm. The study aims to develop a conceptual framework for analysing sustainability across One Health initiatives, interventions, and programs. The review included 38 studies that met the inclusion criteria, focusing on definitions, conceptual frameworks, and analytical frameworks of sustainability. Deductive thematic synthesis revealed key determinants and characteristics of sustainability, highlighting both similarities and differences across sectors. Across the 38 included reviews, we identified characteristics of sustainability existing along a process-outcomes continuum which we further grouped into fifteen process-focused characteristics, and outputs and outcomes that were categorized across a variety of contexts including acute emergency or humanitarian settings as well as within a stable macroeconomic and social construct. The review identified that sustainability has over time become more well defined and evaluated within the human health sector, with fewer review studies addressing it for animal and environmental health. Multisectoral studies often integrate the Brundtland Commission’s definition of sustainability, emphasizing social, economic, and environmental dimensions. The findings also highlight the importance of equity, resilience, and systems thinking in sustainability assessments. The analysis in our review underscores the need for a more holistic and integrated approach to sustainability that considers the interconnectedness of human, animals and ecosystems and that addresses the co-benefits and trade-offs across sectors. In our synthesis these concepts were coded from included reviews and mapped onto both the integrated definition and the meta-conceptual framework, ensuring they were structurally embedded into the proposed approach. A new integrated definition of sustainability is proposed, emphasizing quality-assured systems, services and interventions that are just and equitable, while being socially, economically, and environmentally viable, adaptable over time, and optimised for health benefits across humans, animals, and ecosystems without compromising future generations’ well-being. The accompanying evidence derived meta-conceptual framework serves as a normative guide for analysing sustainability in One Health contexts, adaptable across varying scales and health challenges. It is intended for use by policymakers, implementers and evaluators working on multisectoral programmes in human, animal and environmental health, particularly where a trade-off or co-benefit analysis is needed and where integrated approaches are being developed or scaled. Our study offers a robust evidence-based foundation for designing, assessing and implementing sustainable practices across One Health initiatives. Future research should focus on validating and further refining this framework through empirical studies across sectors and diverse One Health contexts. Particular attention should be given to addressing the gaps in sustainability assessments within the animal and environmental health sectors. As global health challenges continue to evolve, fostering a shared understanding of sustainability and promoting cross-sectoral collaboration will be essential for developing resilient and effective health interventions. In an era marked by increasing environmental pressures and shifting geopolitical landscapes, the principles of sustainability and One Health are more relevant than ever. This review contributes to the ongoing discourse on sustainability, providing a roadmap for stakeholders to navigate the complexities of multisectoral collaboration and ensure lasting impacts on global health and well-being across ecosystems.</p>