Mark D. Terjesen, PhD, is a licensed psychologist, professor of psychology in the Department of Psychology at St. John’s University in Queens, New York, a Fellow, Supervisor, and Core Faculty Trainer of Albert Ellis Institute (AEI). Dr. Terjesen serves as the Director of Clinical Training (DCT)/program director of the School Psychology PsyD program and has trained and supervised doctoral students throughout his tenure, having mentored more than 100 doctoral dissertation research projects. Dr. Terjesen has trained many professionals internationally in the use of rational emotive behavior therapy (REBT) and cognitive-behavioral therapy practices with children, adults, and families. Dr. Terjesen has studied, published, and presented at many national and international conferences on topics related to REBT and assessment and clinical work with children, adolescents, and families. His scholarly contributions include serving as the co-author of the books: Deliberate Practice in Behavioral Parent Training and Deliberate Practice in Rational Emotive behavior Therapy and co-editor of the books Rational-Emotive and Cognitive-Behavioral Approaches to Child and Adolescent Mental Health, Cognitive Behavioral Therapy in a Global Context, the Handbook of Training and Supervision in Cognitive Behavioral Therapy, and the Handbook of Behavioral Parent Training. Dr. Terjesen has held numerous leadership roles within local, state, and national organizations and serves as the clinical director at North Coast Psychological Services in Syosset, New York where he maintains a private practice providing clinical work with youth, adults, and families.