The treatment gap can be defined as the difference between the proportion of people who have the disease and the proportion of those who receive proper treatment. The mental disorder treatment gap should be resolved because mental disorders have a substantial socioeconomic burden. This study examined the current status of the mental disorder treatment gap in Korea to identify the strategies to address it. The causes of the mental disorder treatment gap include a lack of human resources, a lack of financial resources, and low mental health literacy. To reduce the treatment gap, improving the medical fee of the psychiatric intervention, improving the quality of the assessment on the psychiatric residency training program, the provision of basic mental health services delivered by primary care physicians, the inclusion of classes on mental health in the school curricula, and the promotion of public’s mental health literacy through the active use of media should be considered. The present article is significant in that it proposed cost-effective measures by adding them to existing systems. The quantitative evaluation of mental health intervention is essential for these methods to be carried out effectively.