To explore how city-level international partnerships can succeed, this study focuses on the sister-city relationship between Wuhan (China) and Manchester (UK), which has demonstrated strong outcomes in sustainability collaboration. Through a detailed analysis of this case, the study identifies three key factors for enduring international collaboration – sustained mutual benefit, broad partnership areas, and deep grassroots engagement – and reveals how they adapt and consolidate over time. These results suggest that international partnerships need to be designed not only to ensure mutual benefit but also to promote inclusiveness and multi-level participation.

The importance of global collaborations in achieving sustainable development is widely recognised. However, establishing and maintaining international partnerships remains a significant challenge. To understand how effective international partnerships can be developed to address sustainability challenges, this study conducts a case study of the Manchester–Wuhan sister-city relationship, a highly successful and representative example of international cooperation on sustainable development. Drawing on insights from 27 semi-structured interviews with stakeholders involved in organising and participating in the initiative, the study shows that the longevity of international partnerships is determined by three core factors: the preservation of mutual benefit, the breadth of cooperation, and profound grassroots involvement. These factors generate both economic and emotional capital, which incentivises governmental and non-governmental actors to deepen their engagement in sustainable urbanisation. This engagement also serves as a buffer against bilateral tensions between the UK and China. These results offer implications for how local initiatives can serve as effective mechanisms for fostering international cooperation in advancing sustainable development.

Building international partnerships for global sustainability requires mutual benefit, inclusiveness, and engagement at multiple levels.