Background: Evidence based treatment interventions for young people with first-episode psychosis (FEP) and trauma histories is lacking. Although case formulation (CF) has been widely regarded in cognitive <span class="attribute-to-highlight medbox">behavioural</span> <span class="attribute-to-highlight medbox">therapy</span> manuals as beneficial, there is limited empirical research examining how clients and therapists experience the process. Aim: This study aimed to explore young people’s reactions to CF in treatment for PTSD (post-traumatic stress disorder) and FEP