This research aimed to develop and initially validate an adolescent personality inventory based on the five factor model. The most well-known and well validated measure of personality is the NEO-PI-R, a 240-item five factor model of personality which requires an adult level of vocabulary. Very few personality inventories have been designed for adolescents, and the majority of research on the five factor model of personality is based on adults. The aim was to produce a personality scale to assess the five factors of Neuroticism, Extraversion, Openness, Agreeableness and Conscientiousness, that (i) comprises a vocabulary that could be understood by contemporary teenagers aged 13 to 18, (ii) is a short-form personality measure, and (iii) is freely available for use by researchers and practitioners. The present study involved 4 phases that led to the development and initial validation of the Adolescent Personality questionnaire (APQ). In Phase 1, focus groups were used to generate 88 items. These items were evaluated by a panel of experts. In Phase 2, the items were administered to a sample of 179 students in grades 8 to 12. Item and exploratory factor analyses reduced the number of items to 50, producing internally reliable subscales. In Phase 3, the APQ was administered to a second sample of 279 students, and in Phase 4 the APQ was administered to a third sample of 405 students. A confirmatory factor analysis led to a final scale of 25 items across 5 subscales that demonstrated sound consistency and validity. Initial validity for the scales is encouraging and further testing of these measures is expected to support their use. Valid but brief assessments are needed in order to understand the role that personality plays in individual differences for adolescent populations. It is expected that the APQ could be used by school counsellors and teachers to help adolescents gain insight into their personality and how it translates into daily behaviour, as a basis for career development and vocational assessment, to target at-risk students for early intervention, and for use in research.