This chapter provides a rationale for the theory of change and accounts for the methodology used to map the global media literacy field to its four dimensions—access, awareness, capability and consequences. To use this theory of change, we first use the 4 element descriptors to identify the kind of change we want media literacy to make—is it to do with people’s access to media? Is it about their media awareness? Is it intending for help people to use media literacy to extend their capabilities in their lives? Does it want to make a positive difference to society through the consequences of people’s media literacy? Often a media literacy project will create change in more than one of these areas, so it is not about only identifying which one element is relevant but looking across the elements to see where change can happen. This framework is also flexible so we can identify change, see the potential for change and include both manifest and latent change. When we have identified the change elements which the media literacy project or activity can achieve, then we move to the more detailed change objectives table and identify how change can be evidenced or where the potential for change is apparent—for example, new kinds of knowledge developed by people taking part in the activities, or people doing things differently in their lives, and how these changes are related to their access, awareness, capability or the consequences of their media literacy. This chapter describes the journey the theory of change has taken, through work with BBC Media Action, the British Council, Global Challenges Research Fund, UK Government, Ofcom and the Media and Information Literacy Alliance. Each iteration of the theory of change is set out, to ‘show the working’ to the point where it can be used, here, to evaluate 400 recent media literacy interventions from all over the planet.