The scientific and practical justifications for transdiagnostic CBT are well known and yet there is no consensus on the theoretical approach that should inform it. In this article, we explain the scientific and practical benefits of using Perceptual Control Theory (PCT) by introducing the theory, discussing how it explains the maintenance of psychological distress, the different ways that distress is manifested across disorders, and reviewing evidence for the theory and its applications. We explain how PCT can inform existing active ingredients of CBT such as exposure, behavioral activation, decentering, formulation, and the therapeutic alliance. We also introduce Method of Levels therapy as a transdiagnostic CBT informed by PCT, and describe the implications for service organization and modes of delivery, understanding help-seeking, and recovery. We conclude by considering limitations and directions for future developments.