In 2012, I project managed a team of researchers who were commissioned to undertake an evaluation of the Sunderland Health Champions Programme. Evaluation is an activity that remains central to health promotion practice because it is concerned with assessing whether interventions are effective. Health Champions are a growing component within the British public health workforce, and their roles are emphasised within the coalition's government's public health strategy. However, there is the need for further exploration of the way in which Health Champions work and the effectiveness of programmes that use Health Champions as a mechanism to try to achieve positive health changes. Therefore, Sunderland Teaching Primary Care Trust commissioned independent researchers, staff from the Centre for Health Promotion Research at Leeds Metropolitan University, to evaluate their Health Champions Programme. This case study provides an account of the evaluation, taking the reader through the methods that were used and in particular focusing upon the use of a theory of change approach that is associated with realistic evaluation as a specific approach. The case sheds light upon the challenges of evaluating practice initiatives as well as highlighting the usefulness of theory of change as an evaluation tool.