This study examined the efficacy of an evidence-based supportive leadership program to address psychosocial hazards identified in an organisational health review of a government department. Participants were employees identified as having supervisory and management roles (N = 57; males = 30, females = 27; age range 22 to 63). The program was implemented systematically over a 6-month period using 2 × 2 day intensive workshops, interim 360 peer review assessment and 1-day follow-up. The program used a variety of behavioural learning approaches with individual and group feedback from professional, peer and self-review. The results showed a major improvement in organisational health with significant changes in risk status across the domains of Relationship, Manager and Peer Support. Improvements in organisational health made within the leadership group had generalised across the entire workforce and continued to be maintained at the 18-month follow-up.