Psychological safety has been hypothesised as an important antecedent of the success of agile software development (ASD) teams. However, there is a lack of investigation on psychological safety in large-scale agile (LSA) software development teams. This study explored the antecedents and effects of psychological safety on LSA teams. We conducted semi-structured interviews with software professionals working on LSA project in a Scandinavian technology company. The results suggest that building a psychologically safe environment is a multi-dimensional factor that requires proactive leadership approach, open communication and constructive feedback. The focus should be on designing teams for learning, remuneration safety, and a well-prepared onboarding process for new team members. A psychologically safe environment contributes to effective teamwork, work satisfaction, and promotion of learning. Absence of such an environment leads to brain drain, highlighting the consequences of neglecting this essential aspect of organisational culture. Future research directions are proposed in this paper.