Purpose: The aim of this study was to provide the first formal evaluation of a unique 12-session group therapy programme developed by the UK-based National Association for People Abused as Children (NAPAC). Method: The therapy outcomes of this programme were assessed using the CORE-OM tool. Clients comprised 26 individuals (7 males and 19 females), with an age range of 19-67 (mean = 41; SD = 12.76). Clients were survivors of sexual, physical, emotional or neglectful childhood abuse, or a combination of these, and were from four different locations: London (n = 9), Bury (n = 4), Belfast (n = 8) and prison (n = 5). Findings: Across all CORE domains, improvements were shown from pre-to post-therapy. No gender or age differences were revealed, and improvements were shown across both community members and prison inmates. Implications: A person-centred approach to group therapy is beneficial to a wide range of adult clients within the community and prison settings that require therapy after historical sexual, physical, emotional or neglectful childhood abuse.