Introduction: In Australia, recent changes in mental health emergency care (MHEC) service delivery models highlight the need for clinicians to increase their knowledge and skills in mental health. A workplace training program was developed and implemented across the state of New South Wales (NSW) between 2009 and 2010. The program focused on the assessment, management, and support of people who present to Emergency Departments with common mental health problems. The study sought to assess whether there was a change in the knowledge, confidence, and skills of clinicians as a result of the workplace training program. Methods: A total of 127 (89.4%) mental health and emergency department staff returned precourse and postcourse surveys that measured their self-reported confidence in specific mental health skills areas, and perceived self-efficacy in dealing with aggressive behaviors. A 15-item researcher-developed test evaluated mental health knowledge. Perceptions of learning and connectedness were also assessed. Differences in scores were measured using parametric (matched pairs t-tests) and nonparametric (Wilcoxon matched-pairs signed-ranks test), with the magnitude of the effect determined using Cohen's d. Results: Despite challenges in ensuring the involvement of emergency department staff, statistically significant improvements (P <0.001) were detected in all confidence and skills questionnaire items, perceived self-efficacy in dealing with aggressive behaviors and the knowledge test, with medium to large effect sizes. Discussion: It is noteworthy that even when delivered primarily with mental health staff the program was highly beneficial. The significant investment in new models of MHEC across NSW and recruitment of less experienced staff highlights a need for further research and implementation of the program.