Trauma in children is a devastating reality with immense psychological impact on the child. Numbers indicate that millions of children experience trauma every year. Outcome research therapy with trauma-exposed children is scarce and mostly focuses on cognitive and behavioural changes. Anecdotal evidence suggests that Lifespan Integration (LI) therapy integrates traumatic experiences into other life experiences leaving them feeling more congruent and renewed. In this research study, we investigate the efficacy of Lifespan Integration with children by means of careful examination of one participant. We applied Robert Elliott’s Hermeneutic Single Case Efficacy Research Design (2002, 2014), which uses quantitative and qualitative data to argue for and against therapy efficacy. The 12-year-old research participant received 8 sessions of LI over three months, and data was collected before, throughout, and after therapy. The extent of the client’s change over the course of therapy was investigated, as well as LI’s contribution to the change, and what parts of LI were most helpful in bringing about change. Findings indicate that the client changed substantially over the course of therapy with lasting effects at follow-up, LI was substantially responsible for this change, and the timeline as an LI specific modality helped to bring this change. Details about trauma-exposed children, the theoretical underpinnings of LI, a detailed description of the HSCED procedure, as well as further directions of LI and HSCED are discussed.