Serious games and simulations are increasingly used in fields such as education, healthcare, defence and business training. Serious games and simulations transcend entertainment games, by offering a platform to engage with complex issues in a safe, controlled environment. However there are also risks associated with serious games and simulations, such as those posed to the psychological safety of learners. In relation to games or simulations, psychological safety refers to being able to engage without fear of negative personal consequences. How do you ensure that a serious game or simulation is safe, and fosters a sense of security and trust? This paper explores the ways that psychological safety can be considered when designing a serious game. By synthesising insights gathered from interviews with multiple acclaimed serious game developers with the current literature regarding psychological safety in serious game and simulation design, specific frameworks, approaches and challenges are examined. By examining these issues, this paper aims to increase the understanding of how various aspects of simulation and game design can impact psychological safety.