Solving individual, group, or societal problems through social intervention in practice settings is a complex task. The extent to which this end is achieved depends heavily on the effectiveness of the change strategies in use. Increased understanding of how these change strategies work to impact outcomes is at the forefront of the science of social intervention. In this special issue, we have gathered a collection of seven articles that present central issues related to program theory in social interventions developed in practice setting. Our goal is to advance the knowledge of how an understanding of theory in practice can advance social intervention research.