This review aimed to examine the effectiveness of mental health training programs designed to improve the knowledge, attitudes, or helping behaviour of secondary school teachers for adolescent depression, anxiety, and related mental health problems. A systematic search strategy was conducted using electronic databases and hand search procedures. Eight studies met inclusion criteria, representing six unique training programs. All eight studies reported an improvement in mental health knowledge (d = 0.57-3.1) and attitudes (d = 0.36-1.18) at post-intervention. There was little evidence that the included training programs improved teachers' helping behaviour or students' mental health. There was no evidence to suggest that these training programs alleviated mental health problems among teachers themselves. Only two studies were conducted as randomised controlled trials. The findings suggest there may be value in providing mental health training to teachers; however, there is an urgent need for more rigorous research to determine which, if any, programs can alter teacher behaviour or improve student outcomes for mental health.