Background: The recently released 11th edition of International Classification of Diseases (ICD-11) included new definitions of disorders specifically associated with stress. Complex post-traumatic stress disorder (CPTSD) was included in ICD-11 as a new trauma-related disorder which could develop following prolonged or reoccurring traumatic experiences. Research on ICD-11 PTSD and CPTSD validity and epidemiology has, so far, mostly been conducted in adult population. This is the first study to explore the construct validity of the Child and Adolescent version of International Trauma Questionnaire (ITQ-CA) as a measure of ICD-11 CPTSD symptoms. Methods: The study was based on a sample of 932 adolescents from the general population aged 12–16 (M = 14.25, SD = 1.27) years exposed to various traumatic experiences. We used confirmatory factor analysis (CFA) and latent class analysis (LCA) to test validity of the ITQ-CA scores from adolescents. Results: The best fitting measurement model included six correlated factors representing the three PTSD and three DSO symptom clusters. LCA analysis revealed four classes whose symptom profiles were reflective of ‘CPTSD’, ‘PTSD’, ‘DSO only’, and ‘Baseline’. Conclusions: Findings of the study provide support for the construct validity of the ICD-11 models PTSD and CPTSD among adolescents.