The role of adolescent personality concerning mental health, well-being, self development, and academic performance is an interesting aspect that needs more attention. The use of the JTCI (Junior Temperament and Character Inventory) can contribute to more knowledge and a better understanding of a possible influence of personality in this context. The aim of this study was to assess the psychometric properties of the Norwegian version of the JTCI among an adolescent sample in terms of factor analysis, reliability and validity. The sample included 2075 subjects in the age from 15-18 years. We analyzed the factor structure, internal consistency, and validity of the measure. The Norwegian version of the JTCI was found to have good psychometric properties in terms of internal consistency, a reasonable factor structure and significant correlations with depression, self-esteem, and self-efficacy. However, further research on its differentiation of Harm Avoidance and Self-directedness is needed. The JTCI appears as a useful tool in addressing issues ranging from scholastic performance to developmental issues, mental health and well-being.