BACKGROUND: Traumatic experiences in childhood can have far-reaching and serious consequences for the development of those affected. Little is known about the age- and sex-specific symptom patterns in children and adolescents following a traumatic event. These do not always manifest in symptoms that meet the diagnostic criteria for post-traumatic stress disorder according to ICD 10. METHODS: In an outpatient cohort of 84 children and adolescents aged 6 to 18 years, we utilised the dimensional Child Behaviour Checklist (CBCL) to analyse symptoms occurring within twelve months of a traumatic event as defined in ICD 10. Regression models were applied to examine the effects of sex, age, and their interaction. CBCL (sub-)scales from caregivers served as the outcome variables. RESULTS: The most severe symptoms were externalising symptoms found in boys aged six to below twelve years, while girls of the same age showed the fewest symptoms. No fully consistent picture regarding age- and sex-effects was found across the (sub-)scales, however, the most consistent finding for all scales was an interaction between age and sex, resulting in a convergence between boys and girls with age. Adolescent males and females were affected to a similar extent. CONCLUSION: Knowledge of age- and sex-specific patterns in children and adolescents following a traumatic event is essential to recognise possibly trauma-related symptoms at an early stage, initiate adequate treatment. Considering that trauma can exacerbate or complicate externalising symptoms, and vice versa, it is crucial to integrate trauma-specific interventions into the treatment plan for those affected. Developing comprehensive, age- and sex-specific diagnostic criteria for trauma-related disorders might not only improve early detection and treatment but also ensure that interventions address both emotional and behavioural dimensions effectively. Future research should focus on refining these criteria and exploring the interplay between trauma and co-occurring conditions to enhance treatment outcomes.