This article addresses the need to clearly understand professional responsibility and the critical role it plays in the lives of individuals with intellectual and developmental disabilities (IDD), in shaping professions for the better, and in enhancing the functioning of society for the benefit of all. Understanding professional responsibility is especially timely during the current transformation that is occurring in the field of IDD. To that end, the article discusses what is a profession, who is a professional, and what is professional responsibility. Using a logic model framework, the article describes the components of professional responsibility that include its building blocks such as respect for the person, professional ethics and standards, critical thinking skills, and clinical judgment; its use of nine professional practices including empowerment, evidence-based practices, individualized supports, and person-centered outcome evaluation; its outcomes in terms of mutual trust, the improved effectiveness of clinical functions, and professional accountability; and its impacts regarding individual benefit, professional integrity, and societal enhancement.