Although mental health problems increase markedly during adolescent years, therapists often find it difficult to engage with adolescents. The majority of disturbed adolescents do not receive professional mental health care and of those who do fewer still will fully engage with the therapeutic process (Offer et al. 1991; US Surgeon General 1999). Personal Investigator (PI) is a 3D computer game specifically designed to help adolescents overcome mental health problems such as depression and help them engage more easily with professional mental health care services. PI is an implementation of a new computer mediated model for how therapists and adolescents can engage. The model has its theoretical foundations in play therapy and therapeutic storytelling and applies current research on the educational use of computer gaming and interactive narrative systems to these foundations. Previously demonstrated benefits of computer games and interactive narrative systems in education include increased motivation, increased self-esteem, improved problem solving and discussion skills and improved storytelling skills (Bruckman 1997; Bers 2001; Robertson 2001; Robertson and Oberlander 2002; Bers et al. 2003; Squire 2003). PI aims to take advantage of these benefits in a mental health care setting. PI incorporates a goal-oriented, strengths based model of psychotherapy called Solution Focused Therapy (SFT). By engaging adolescents, in a client-centred way, it aims to build stronger therapeutic relationships between therapists and adolescents. PI is the first game to integrate this established psychotherapy approach into an engaging online 3D game. Results of trials of PI with four adolescents, referred to clinics for issues including anxiety and behaviour problems, attempted suicide, and social skills difficulties, are presented. ; Full-text of this article is not available in this e-prints service. This article was originally published following peer-review in Interactive Technology and Smart Education, published by and copyright Emerald.