Two proponents of theory-based approaches to evaluation that have found favour in the UK in recent years are Theories of Change and Realistic Evaluation. In this article we share our evolving views on the points of connection and digression between the approaches based on our reading of the theory-based evaluation literature and our practice experience. We provide a background to the two approaches that emphasizes the importance of programme context in understanding how complex programmes lead to changes in outcomes. We then explore some of the differences in how `theory’ is conceptualized and used within the two approaches and consider how knowledge is generated and cumulated in subtly different ways depending on the approach that is taken. Finally, we offer our thoughts on what this means for evaluators on the ground seeking an appropriate framework for their practice