--- - |2- Abstract The transtheoretical model and the stages of change are often used to adapt treatment to the individual client. The aims of this study were to review the stages of change and popular measures of change readiness in psychotherapy and to conduct a meta‐analysis of the relation between readiness measures and psychotherapy outcomes. We report data from 76 studies, encompassing 25,917 patients. Moderate‐sized effects (d = 0.41) were found for the association among multiple disorders, including substance and alcohol use, eating disorders, and mood disorders. Outcomes were a function of the pretreatment stage of change; that is, the farther a patient along the stages, the better the treatment outcomes. This review added 37 studies to the data reported in 2010, further strengthening the link between readiness and therapy outcomes. The article concludes with limitations of the research, diversity considerations, and therapeutic practices for stage matching in psychotherapy specifically and behavioral health more generally. - Journal of Clinical Psychology, EarlyView.