This chapter begins by outlining the research that links perfectionism with anxiety symptoms, disorders, and treatment response in children. It examines factors that may influence and explain why perfectionism is connected with child anxiety. The chapter reviews research that pertains to total anxiety symptoms, rather than specific diagnoses, because the majority of studies examining perfectionism and anxiety in childhood use scales that assess total anxiety symptoms. Evidence from numerous studies supports the notion that perfectionism is a risk and maintenance factor for the development of anxiety symptoms in children. In the only examination of the role of perfectionism in the treatment for children diagnosed with an anxiety disorder, Mitchell, Newall, Broeren, and Hudson found that pre-treatment self-oriented perfectionism predicted poorer treatment outcome for a group of children receiving cognitive-behavioral treatment (CBT). Perfectionism has been hypothesized to interfere and undermine effective treatment and prevention by creating unrealistic standards for coping in the patient.