Background: Globally, promoting mental health and wellbeing among adolescents has become a public health priority, especially for adolescents living with a chronic condition (CC) as research suggests they may be more at risk of developing mental health co-morbidities. Valid and reliable instruments are needed to measure and better understand mental health and mental wellbeing among adolescents living with a CC. To this end, we reviewed studies reporting on mental health and well-being instruments used in adolescent populations living with a chronic physical condition/disease globally.Methods: We used a systematic review method guided by PRISMA to identify assess mental health and mental wellbeing instruments used in adolescents living with a CC. In this instance, mental health instruments were defined as those representing negative domains of mental health (i.e. depression and anxiety) while mental wellbeing instruments included positive aspects of mental health (i.e. self-concept and resilience). Results: We identified 22 articles, which include 31 instruments that were used to measure either mental health (n= 8) or mental wellbeing (n= 15) or both (n=8) in adolescents living with a CC. Of these, thirteen studies used a Health-Related Quality of Life (HRQoL) scale to measure mental health and/or mental well-being; and three studies used. The KIDSCREEN questionnaires and the Strengths and Difficulties Questionnaire were identified as being frequently used across the 22 studies. Additionally, 7 out of the 31 instruments were disease specific, with 3 focusing on adolescents with diabetes. All the instruments were developed in high income countries and adapted for use in lower- and middle-income countries (LMICs). Adolescents with Type 1 Diabetes (n=7) and HIV (n=4) were researched in 11 out of 22 studies. Only eight studies were conducted in LMIC, of which four were in Africa. Conclusions: The findings suggest that HRQoL instruments seem to be useful in measuring mental health - and wellbeing in adolescents living with a CC. Relatively few valid measures of mental health and mental wellbeing for adolescents living with a CC exist generally, which confirms the paucity of research on mental health and mental well-being of adolescents who are living with a CC. There is a need for measures to be developed in LMIC where cultural contexts differ greatly and affects well-being in unique ways.Systematic review registration: PROSPERO CRD42020186707