Emergency services are under enormous pressure to offer programmes that could protect their staff from the psychological impact of stressors encountered in their roles. There has been a surge in the number of pre-incident training programmes aimed at first responders to maintain their psychological wellbeing after critical incidents. These include pre-employment screening programmes, psychoeducation, operational training, line manager training and interventions aimed at improving resilience, wellbeing or stress management. Whilst developed with the best intentions, these programmes vary in efficacy. Therefore, knowing what training to offer first responders prior to exposure to critical incidents is far from clear. In this review, we critique the available evidence and make recommendations about what to offer and what to avoid offering first responders prior to exposure to critical incidents. We found no evidence of the effectiveness of pre-employment screening or psychoeducation offered as a standalone package, and little evidence for interventions aimed to improve wellbeing and resilience to stress - although current trials of empirically-driven interventions for first responders are underway and show promise in preventing stress-related psychopathology. Operational and line manager training showed the most promise but need to be evaluated in high quality trials with sufficient follow-up to draw conclusions about their preventative benefits.