Background: Finding precise definitions of secondary traumatic stress, vicarious traumatization, and compassion fatigue is not easy. While some researchers define these terms differentially, others use them interchangeably. In the present review, we refer to all three phenomena as secondary traumatization.Objectives: This systematic review aims to provide an overview of prevalence rates of secondary traumatization in first responders and to shed light on corresponding resilience and risk factors.Methods: After identifying 219 studies within the searched databases and 2192 references via hand searching, 31 studies were included in this review. We systematically searched the electronic databases PubMed, PsychINFO, and PSYNDEX (German database). The following inclusion criteria were applied: (1) participants had to be first responders working on-site: police officers, firefighters, search and rescue personnel, or emergency and paramedic team members; (2) secondary traumatization (secondary traumatic stress/vicarious traumatization/compassion fatigue) was assessed quantitatively with a validated questionnaire or subscale explicitly measuring secondary traumatization; and (3) English or German language original papers.Results: We found low levels of secondary traumatization in first responders. Several studies describe protective and risk factors for secondary traumatization, including pretraumatic (e.g. age, gender), peritraumatic (e.g. exposure, emotional exhaustion), and post-traumatic factors (e.g. social support, alcohol and tobacco use).Conclusion: Next to an immunizing effect, the low prevalence of secondary traumatization in first responders could be explained by social desirability and job-loss concerns. Therefore, we may be underestimating the prevalence of secondary traumatization in first responders. Some resilience (social support) and risk factors (female gender) are consistent with previous research in other populations. However, owing to the cross-sectional study designs, we must interpret resilience and risk factors with caution. Future research should focus on longitudinal study designs and preventive as well as curative interventions.