Although patients’ psychotherapy outcome expectations correlate with posttreatment outcome, there is limited research explicating treatment elements that causally influence these expectations. Most relevant studies have focused on varied deliveries of a treatment rationale. Although elements of rationale delivery appear important for altering patients’ expectations, many studies have been marked by methodological shortcomings, such as lack of a control group. In this clinical analogue experiment, I examined the influence of expectancy persuasion methods, delivered in a video-based presentation of a cognitive-behavioral treatment rationale for social anxiety, on analogue patients’ post-rationale treatment beliefs, treatment motivation, social anxiety symptoms, and therapeutic action. One hundred and seventy-eight undergraduates screened for elevated social anxiety, and matched for sex and treatment history, were randomized to the experimental (rationale plus expectancy persuasion video) or comparison (rationale only video) group. Consistent with my hypotheses, there were significant increases across both groups in anxiety change expectations, perceived confidence in using CBT exposure techniques to address social anxiety, and perceived helpfulness of exposure techniques. Counter to my predictions, no other effects of time, group, or their interaction emerged for the various dependent variables. Additionally, exploration of socioeconomic status, conceptualization of social anxiety, and initial anxiety change expectations as potential moderators of group effects on the dependent variables revealed no significant findings. The results underscore the clinical importance of delivering a clear treatment rationale; however, they also suggest that the specific methods for persuading patients’ treatment beliefs and activities may have lacked sufficient potency to augment the effects of general rationale delivery.