This article presents 4 studies (N = 1,413) describing the development and validation of the Child and Adolescent Mindfulness Measure (CAMM). In Study 1 (n = 428), the authors determined procedures for item development and examined comprehensibility of the initial 25 items. In Study 2 (n = 334), they reduced the initial item pool from 25 to 10 items through exploratory factor analysis. Study 3 (n = 332) evaluated the final 10-item measure in a cross-validation sample, and Study 4 (n = 319) determined validity coefficients for the CAMM using bivariate and partial correlations with relevant variables. Results suggest that the CAMM is a developmentally appropriate measure with adequate internal consistency. As expected, CAMM scores were positively correlated with quality of life, academic competence, and social skills and negatively correlated with somatic complaints, internalizing symptoms, and externalizing behavior problems. Correlations were reduced but generally still significant after controlling for the effects of 2 overlapping processes (thought suppression and psychological inflexibility). Overall, results suggest that the CAMM may be a useful measure of mindfulness skills for school-aged children and adolescents.