This study identifies factors that support the sustainability of interventions implemented to enhance responses to alcohol and other drug misuse in Australian community health settings. Eight completed projects that had received time-limited funding were sampled to reflect a mix of project types, contexts and success in meeting funding objectives. Projects were investigated using a case study approach involving thematic analysis. Project records were analysed and interviews were conducted with stakeholders to identify intervention elements that continued after funding ceased, and factors that supported this sustainability. Key factors identified were: embedding changes in the operations of the agency; filling a critical gap in the sector; building support from key individuals and agencies; and planning realistically for future ownership. We argue that complexity theory provides a framework to understand both the context-bound nature of intervention sustainability and differences within the literature as to how sustainability is typologised. Each factor associated with intervention sustainability identified in this study reflects an astute understanding of project context and a capacity to adapt. These factors could assist people designing interventions with time-limited funding to maximise ongoing impact of interventions. They should optimally be implemented within an overall approach of flexibility and sensitivity to context.