This study presents the development and psychometric validation of a Career Identity Questionnaire for vocational school students aged 15–19 years. Career identity was conceptualized as comprising career exploration and career commitment, based on theories of identity development and career guidance. Two studies were conducted. In Study 1 (N = 188), principal component analysis (PCA) was used to determine the final structure of the questionnaire. From an initial pool of 20 items, 14 items were retained: 8 items for career exploration and 6 items for career commitment. The two scales were positively correlated (r = 0.48, p < 0.01), with Cronbach’s alpha coefficients of 0.78 and 0.88, respectively. In Study 2 (N = 293), convergent and structural validity were examined using correlation analysis, canonical correlation, ANOVA, and confirmatory factor analysis (CFA). The CFA supported a three-factor structure consisting of exploration within the educational profile, exploration outside the educational profile, and career commitment. Career exploration correlated with school satisfaction (r = 0.31), subjective well-being (r = 0.26), and school success (r = 0.14), while career commitment showed stronger associations with the same variables (r = 0.56, 0.27, and 0.15, all p < 0.01). Canonical correlation analysis indicated significant relationships between career identity dimensions and mental health, with the strongest weights observed for career commitment (r_s = −0.96) and career exploration (r_s = −0.60), explaining 14% of the variance in mental health, while mental health explained 23% of the variance in career identity. Students with below-average values of commitment and exploration reported lower school success, satisfaction, and well-being. The findings provide evidence for the reliability and validity of the questionnaire, supporting its use in both research and practice in educational settings.