Few studies have examined the self-reported mental health of children with an acquired brain injury (ABI). The current study aimed to: 1) identify levels of child-reported depressive and anxiety symptoms and poor self-concept, 2) investigate demographic and injury-related factors associated with children’s mood and self-concept, and 3) examine associations between children’s self-reported mental health and parents’ reports of children’s emotional and behavioral functioning in children specifically with traumatic brain injury (TBI). 122 children (66% male) aged 8–16 years with ABI of mixed etiology were consecutively recruited through an outpatient rehabilitation clinic. Children were administered the Beck Youth Inventories – Second Edition, and parents completed the Adaptive Behavior Assessment System and the Child Behavior Checklist (CBCL). Relative to the norms, 16.4% of children scored in the clinical range for the depression and anxiety scales, and 24.6% reported clinically low self-concept. Children with lower functional status had greater anxiety symptoms. Older children (13–16 years) reported significantly higher depressive and anxiety symptoms and lower self-concept than younger children (8–12 years). A significant interaction between age and sex indicated that older girls reported greater depressive and anxiety symptoms than younger girls whereas no age-based differences were found for boys. Parent-reported total emotional and behavioral problems were positively associated with children’s self-reported depressive and anxiety symptoms and were negatively correlated with self-concept. These findings indicate that adolescents, particularly girls, may be at heightened risk of poor mental health following ABI. Further research investigating the reasons for these demographic differences may inform developmentally sensitive interventions.