This paper provides an overview of the National Mental Health Benchmarking Project (NMHBP) which explored the value of benchmarking within the four main program areas of public sector mental health (general adult, child and adolescent, older persons and forensic). The NMHBP involved a series of forums which enabled participating organizations to benchmark themselves against each other, with a view to understanding variability in performance against a range of key performance indicators (KPIs). Method: Twenty-three mental health organizations took part in the NMHBP. The forums culminated in each mental health organization documenting its performance against relevant KPIs. The processes, impacts and outcomes of the NMHBP were evaluated via a multi-methods evaluation.