The present work seeks to examine the importance of expectancies in computer-mediated treatment and training programs. Two studies examining the role of patient and trainee expectations are presented. Study 1 investigated how expectations of a training game for military surgical teams influence training performance outcomes. The findings have implications for the administration of game-based treatment and training systems. Study 2 explored how pre-treatment expectancies influence post-treatment reactions to a game-based intervention for post-traumatic stress disorder (PTSD). Results indicate that self-efficacy plays a mediating role in the relationship between expectancies and reactions. Together, these studies offer implications regarding the critical role of attitudes towards game-based training and treatment mechanisms.