The evidence-based culture of modern mental health policy and service delivery is being extended through funded efforts to accelerate implementation of research findings in practice settings. In this paper, we argue that this linear model of research and policy-making is profoundly ill adapted to the nature of practice realities and real-world policy-making processes. Both need to be re-conceptualised using the theoretical and practical resources deriving from modern complexity theory. A short case study illustrates the nature of ‘complexity’, the reframing of the notion of ‘evidence’ it implies and the different relationship between research, practice and policy that flows from this more attuned model of mental health and therapeutic processes.