A self-report measure of metacognition for both children and adolescents (ages 7-17) (Metacognitions Questionnaire for Children; MCQ-C) was adapted from a previous measure, the MCQ-A (Metacognitions Questionnaire for Adolescents) and was administered to a sample of 78 children and adolescents with clinical anxiety disorders and 20 non-clinical youth. The metacognitive processes included were (1) positive beliefs about worry (positive meta-worry); (2) negative beliefs about worry (negative meta-worry); (3) superstitious, punishment and responsibility beliefs (SPR beliefs) and (4) cognitive monitoring (awareness of one's own thoughts). The MCQ-C demonstrated good internal-consistency reliability, as well as concurrent and criterion validity, and four valid factors. In line with predictions, negative meta-worry was significantly associated with self-reports of internalizing symptoms (excessive worry and depression). Age-based differences on the MCQ-C were found for only one subscale, with adolescents reporting greater awareness of their thoughts than children. Adolescent girls scored higher on the total index of metacognitive processes than adolescent boys. Overall, these results provide preliminary support for the use of the MCQ-C with a broader age range as well as an association between metacognitive processes and anxiety symptomatology in both children and adolescents, with implications for cognitive behavioral interventions with anxious youth.