Critical to effective fire management is the protection and preparedness of highly trained wildland firefighters who routinely face extreme physical and psychological demands. To date, there is limited scientific evidence of psychosocial education intervention effectiveness in this context. The objective of the current study is to utilise a cluster randomised control trial study design to evaluate fitness training and psychosocial education intervention programs across a wildland fire season. Wildland firefighters (n = 230) were randomly assigned by their work location to one of four experimental conditions. Pre- and post-season assessments of primary (e.g. psychosocial risk factors, physical fitness and psychological capital) and secondary (e.g. work engagement, job stress and incidence of injury) outcomes facilitated comprehensive evaluation. The psychosocial education intervention program was effective at buffering participant appraisals of 12 of 13 psychosocial risk factors, namely: organisational culture, civility, psychological demands, balance, psychological support, leadership expectations, growth and development, influence, workload management, engagement, protection and safety. Participants in the psychosocial education intervention also reported lower stress relating to organisational support compared with those who not receiving the intervention program. Wildland firefighters receiving either or both intervention programs reported a significantly lower incidence rate of injury (9.9%) compared with the organisation’s 5-year average (16.0%).