Mindfulness-based programs for adolescents have become increasingly popular, in line with preliminary evidence supporting their positive effects on psychological functioning. More studies are needed to establish the validity of mindfulness measures for adolescents, in particular with regard to gender differences. This study used confirmatory factor analysis to test the factor structure, reliability, and validity of the recently developed Child and Adolescent Mindfulness Measures (CAMM) with non-clinical adolescents aged 12 to 15 years (N = 562). Additionally, the study aimed to assess the internal consistency of the CAMM with this sample and to determine its convergent validity. All analyses were conducted for the entire sample as well as for males and females separately. Results confirmed the one-dimensional factor structure of the CAMM and the internal consistency of the ten CAMM items, and there were no significant gender group differences. The convergent validity was also supported, with significant correlations between CAMM scores and measures of psychological functioning/distress in the expected directions. When considering correlations separately by gender, mindfulness was weakly but significantly correlated with positive affect in females but not in males. All other correlations were comparable across gender. Overall, the CAMM appears to be a reliable and valid mindfulness measure for both boys and girls.