Routine outcome measures are now being designed for session-by-session use, with emphasis on clinically meaningful items and sensitivity to change. Despite an increasing mental health service focus for young people aged 12-25 years, there is a lack of outcome measures that are designed to be used across this age group. Consequently, MyLifeTracker (MLT) was developed as a brief mental health outcome measure designed for young people for routine use. It consists of the following five items targeting areas of importance to young people: general well-being, day-to-day activities, relationships with friends, relationships with family, and general coping. Participants and methods: The measure was tested with 75,893 young people aged 12-25 years attending headspace centers across Australia for mental health-related issues. Results: MLT showed a robust unidimensional factor structure and appropriate reliability. It exhibited good concurrent validity against well-validated measures of psychological distress, well-being, functioning, and life satisfaction. The measure was further demonstrated to be sensitive to change. Conclusion: MLT provides a psychometrically sound mental health outcome measure for young people. The measure taps into items that are meaningful to young people and provides an additional clinical support tool for clinicians and clients during therapy. The measure is brief and easy to use and has been incorporated into an electronic system that routinely tracks session-by-session change and produces time-series charts for the ease of use and interpretation.