This study explored the process of identity adjustment following adolescent brain injury, within the systemic context of the parent–adolescent dyad. Six young people with an ABI (mean age 16.5 years, range 15–18 years; TBI: n = 3) were individually interviewed, and six respective mothers (mean age 45 years, range 37–50 years). A novel relational qualitative grounded theory approach was used, with analyses of dyads linked in an attempt to capture the shared process of adaptation post-injury for young people and their parents. Shared themes emerged for adolescents and mothers regarding “continuity and change” and “acknowledging or rejecting” experiences of change post injury. Adolescents experienced change as an, at times, distressing sense of being “not normal”. While mothers turned towards their child, working hard to try to “fix everything”, adolescents sought continuity of identity in the context of peer relationships, withdrawing socially to avoid feeling abnormal, reframing or finding new relationships. Some mothers sought to fill social losses through family or disability-specific activity. This study provides a relational understanding of the process of identity adjustment post adolescent BI. Future research and clinical practice should recognize the significant work of mothers, and significance of social relationships to adolescents’ emerging post-injury identity.