The Adolescent and Adult Mindfulness Scale (AAMS; Droutman et al., 2018) was developed to provide a multifaceted measure of mindfulness that can be used for both adolescents and adults. It is a 19-item scale that measures mindfulness as a combination of four key components: (1) awareness of the present moment, (2) non-reactivity, (3) non-judging predisposition, and (4) self-acceptance. The scale was validated across five studies for which both adolescents and adults were recruited. Confirmatory factor analyses revealed a good fit of a four-factor model for both adolescents and adults. Tests of measurement invariance revealed that the factor structure and psychometric characteristics were similar across age groups, indicating that the meaning of the subscales are consistent across adolescents and adults. The scale demonstrated good internal and temporal reliability and converged with a separate well established measure of mindfulness. Consistent with the theoretical role of mindfulness in emotion regulation, AAMS scores converged with a measure of emotion regulation, and correlated with academic success and family functioning. Scores also correlated with a measure of self-compassion. Moreover, AAMS scores increased after exposure to a mindfulness intervention adapted for adolescents, suggesting scale sensitivity to intervention effects. Results suggest that the AAMS is a valid measure of mindfulness and its components in both adolescents and adults, thus both the full scale and individual subscales can be used for assessment.