Clients with generalized anxiety disorder (GAD) that demonstrate observer-coded treatment ambivalence benefit from the addition of motivational interviewing (MI) to cognitive behavioral therapy (CBT; Button, Westra, Constantino, & Antony, 2016). While observer-coded assessment of ambivalence and readiness for change is resource-intensive, the present study investigates the use of more efficient self-report measures to predict treatment outcomes. Participants (
N= 85) with GAD received CBT or MI-CBT and completed self-report measures of readiness for change (Change Questionnaire, Miller & Johnson, 2008) and ambivalence (Treatment Ambivalence Questionnaire, Purdon, Rowa, Gifford, McCabe, & Antony, 2012). Greater self-reported baseline readiness for change was associated with lower posttreatment worry and symptom severity and faster reduction in worry. Self-reported ambivalence was not associated with outcomes. Patients with less concern about adverse consequences of treatment who received CBT experienced greater increases in readiness for change than those receiving MI-CBT. We discuss implications for using these measures in clinical settings.