Instruction in Functional Assessment introduces learners to functional assessment (FA), which includes a variety of assessment approaches (indirect, observational, and experimental) for identifying the cause of an individual’s challenging behavior for the purpose of designing effective treatments. FA is mandated by federal law and is a recognized empirically based approach to treatment of individuals with challenging behaviors (e.g., disruptive, self-injurious, and aggressive behaviors). Instruction in FA is essential for students who will one day enter professions as educators, psychologists, social workers, counselors, or mental health professionals.The purpose of this textbook is to provide instruction in FA skills for pre-professionals in the fields of education and psychology. This supplemental resource provides the context, background, and knowledge to facilitate students’ acquisition of the methods, decision-making, and skills involved in conducting FA. Each chapter begins with focus questions designed to promote reflective thinking and ends with discussion questions. To promote application of FA in diverse situations and teach important lessons, case studies of individuals with challenging behaviors, interactive activities, and opportunities for practice are embedded in the chapters. Moreover, the text includes the ingredients to facilitate students’ role play and rehearsal of appropriate FA skills while working in cooperative groups and using performance-based training.