This study examined the role of theoretically meaningful mediators of therapeutic change—interpretation bias, perceived control, and coping strategies—in a cognitive-behavioral intervention for anxious youth. This is one of the few studies that examined the change in potential mediator and outcome variables by means of a longitudinal design that included four assessment points: pretreatment, in-treatment, post-treatment, and at 4-months follow-up. Forty-seven 8- to 12-year-old children with a principal DSM-IV diagnosis of anxiety disorder participated in the study. On each assessment point, questionnaires assessing the mediator variables and a standardized anxiety scale were administered to the children. The results showed that perceived control and interpretation bias (but not coping strategies) accounted for a significant proportion in the variability of various types of anxiety symptoms, providing a preliminary support for the notion that these cognitive dimensions’ act as mechanisms of therapeutic change in cognitive-behavioral therapy for anxious children.