The science-informed approach to clinical practice is founded upon ongoing quality improvement and involves key skills that allow clinical psychologists to confidently provide services in a competitive health care market. Thus, programme evaluation is a core clinical psychology competency but needs to be provided via a co-design framework. The chapter outlines how co-designed programme evaluation addresses patients’ needs in five steps: (i) asking the right questions, (ii) developing an evaluation plan, (iii) collecting and analysing data to produce usable findings, (iv) translating the findings into recommendations for action, and (v) advocating and promoting change. The chapter illustrates how empirically-based programme evaluation supports accountable clinical practice, both at the level of the individual patient and at the aggregate level of the service provider or agency.