This article describes a comprehensive framework for incorporating moderator and mediator variables in program logic models and theory development as a useful way to better implement and evaluate policies and practices in the field of intellectual and developmental disabilities related (IDD). Firstly, an overview of [program] logic models in the field of IDD is provided. Secondly, we present the role of moderator and mediator variables in program logics models. Thirdly, the role of moderators and mediators is explained in relation to outcomes through a systematic review in the Web of Science. Fourthly, a discussion about the role that moderator and mediator variables play in theory development is presented. Fifthly, a comprehensive framework for incorporating moderator and mediator variables into program logic models is proposed. This comprehensive framework involves testing specific relations between well-defined and operatized moderator and/or mediator variables that may influence and impacts policies and practices' outcomes. When mediators and moderators are considered and included in program logic models, the effect of interventions, practices and policies can be better understood and therefore enhanced.