There is growing interest in perfectionism among children and adolescents as well as growing interest in the measures designed to assess perfectionism in young people. The current article describes the development and psychometric characteristics of the Child–Adolescent Perfectionism Scale (CAPS), a measure that assesses self-oriented perfectionism and socially prescribed perfectionism. The results of three studies involving multiple samples are reported. The psychometric features of this measure are summarized, including extensive data that attest to the reliability and validity of the CAPS subscales. Normative data are also provided in Study 1. The results of Study 2 suggest that the academic behavior of perfectionistic students is motivated by a complex blend of factors that include a strong emphasis on introjected regulation in both self-oriented and socially prescribed perfectionism; however, there are key motivational differences between these perfectionism dimensions. Finally, Study 3 confirmed that self-oriented and socially prescribed perfectionism are associated with various indices of stress, distress, and maladjustment. Collectively, our results support the use of the CAPS and the notion that vulnerable children and adolescents who are perfectionistic are under substantial pressure to meet expectations. The assessment and theoretical implications of these results are discussed.