In the twenty-first century, it is more obvious than ever before that health services research and its practitioners exist in an extremely complex contextual environment. Consequently, at the heart of understanding how to develop interventions in a setting characterized by multifaceted health care demands, is the realization that no one research method in isolation will suffice. In this chapter an overview of mixed methods and their potential contribution in undertaking research on complex interventions (Medical Research Council, 2008) will be provided.