Co-opetition is gaining increasing attention as a potentially useful form of inter-organisational collaboration model to improve firms’ sustainable performance. However, limited previous studies have provided a clear substantive theory or offered empirical evidence for the process of sustainability-driven co-opetition. This paper explores how competing companies can collaborate in their supply chains (SCs) to achieve a higher level of sustainability performance by identifying drivers, facilitators and barriers of co-opetition. Based on two explorative case studies of co-opetition in the UK, the findings of this paper lead to a number of propositions and a theoretical framework for sustainability-driven co-opetition in SCs. This study contributes to the literature by providing a more in-depth understanding of co-opetition as a strategic capability for firms. This paper also proves the feasibility of a combined use of Resource-Based View and Network Theory perspectives in explaining a paradoxical inter-organisational relationship like co-opetition. A road map for sustainability-driven co-opetition in SCs is also provided as a heuristic decision model for practitioners.