Theory-driven implementation and evaluation of pharmacy services can enhance their contribution to overall healthcare. As complex interventions most pharmacy practice programmes and services will be adopted and modified during their implementation into various healthcare contexts and systems. Realist approaches to theory-driven evaluation consider these variations in programmes, interventions and the contexts of their implementation and establish theories on how they work best, for whom and why. This paper illustrates the practical application of the realist philosophy of science to pharmacy practice relevant areas of healthcare using two case studies, a realist synthesis of existing literature on medication reviews and a realist review and evaluation related to medicines management. Applying realist logic establishes causative explanations of what could be essential factors in the success of programmes, enabling policy makers in their decision-making and pharmacy practice researchers as well as practitioners in optimising service design.