The purpose of this study was to assess the psychometric properties of a newly devised instrument, the Adolescent Health Promotion scale (AHP), a 40-item Likert-type self-report instrument used to detect unhealthy lifestyles in adolescents. Content validity was considered to be supported based on the findings of previous studies and the observations of a panel of 14 content experts. This study examined the construct validity and reliability of the instrument. The psychometric properties of the AHP, including item analysis, factor analysis, and reliability measures, were assessed based on the responses of 1,128 Taiwanese adolescents. Kaiser-Meyer-Olkin (KMO) measures and Bartlett's sphericity test showed that the samples met the criteria for factor analysis. Factor analysis yielded a six-factor instrument that explained 51.14% of the variance in the 40 items. The six factors were social support, life appreciation, health responsibility, nutritional behaviors, exercise behaviors, and stress management. The Cronbach alpha reliability coefficient for the total scale was 0.932, and alpha coefficients for the subscales ranged from 0.75 to 0.88. The results of this study indicate that the AHP has good construct validity and reliability in Taiwanese and that its use by school health nurses to assess adolescent health promotion programs is warranted.