To evaluate group supervision implementation fidelity in the Strengths Model of case management within one adult mental health service. A fidelity audit was undertaken to analyse data across three service settings-residential and community-during the initial three months, utilising instruments developed by Rapp and Goscha (The Strengths Model: Case management with people with psychiatric disabilities, vol 2. Oxford University Press, New York, 2006). Very high fidelity for group supervision was achieved for group interaction (74.8 ), client work (77 ) and by case managers (90 ). A standardised approach to group supervision process and documentation greatly supported fidelity in implementation. The Rapp and Goscha tools had utility as both learning aids and audit instruments.