<p>Self-construal plays an important role in mental health, but there has been only limited evidence from studies in adolescent samples. Research on adolescent self-construal has been hindered by a lack of psychometrically sound measures of self-construal. We investigated the longitudinal invariance and criterion-related validity of the Aspects of Identity Questionnaire-IV (AIQ-IV), a measure developed to assess four identity orientations (personal, relational, public, and collective) posited in the tetrapartite model of the self. The sample included 1340 adolescents (63.9% female, <i>M</i>_age = 16.11) who completed measures at two time points 6 months apart. We found support for the four-factor model obtained using the exploratory structural equation modeling (ESEM), which showed evidence of full scalar invariance across time. The concurrent and prospective associations with subjective well-being and internalizing/externalizing problems provided evidence for criterion-related validity of the AIQ-IV. The four identity orientations showed moderate to high stability over 6 months. Our findings suggest that the AIQ-IV may be a useful tool for assessing adolescent self-construal.</p>