Globally, promoting mental wellbeing among adolescents is of great public health and social significance. However, less is known about advances in measures of mental wellbeing, relevant for use in mental health interventions, which are age-appropriate and acceptable for use among adolescents. Comprehensive assessment includes multiple aspects of mental wellbeing, as well as positive indicators of feeling and functioning. This review used systematic review methods, guided by PRISMA, to identify and assess comprehensive instruments in terms of their content, conceptual relevance for youth, and responsiveness to change. Ryan and Deci’s framework for mental wellbeing, grounded in hedonic and eudaimonic perspectives, was applied to assess the preponderance of feeling and functioning items for each instrument. The review identified 11 instruments that fit specified inclusion criteria. Only four of the scales were developed for adolescents. Though the scales varied in their preponderance of items, all scales encompassed at least one indicator of both feeling and functioning. Findings emphasize the importance of validating adult-developed instruments for youth and ensuring the instrument’s cultural and conceptual relevance within groups of adolescents. As promoting mental wellbeing becomes critical to the field of practice, practitioners need access to relevant and acceptable measures.