Mental health literacy is essential for the recognition, management, and prevention of mental disorders among school-aged children. However, few studies have examined the implementation status of school-based mental health literacy in Asian countries. This study aims to compare the approaches taken by the Philippines, Indonesia, and Japan in managing school-based mental health literacy through curriculum-related policies. The collected documents of this study analyzed both policies (formulated from 2000 to 2023) and curricula (from grade 1 to grade 12) that were adapted to the deductive content analysis methods. This study highlights two key findings on school-based mental health literacy. First, mental health literacy is incorporated into health and physical education in Japan, health, values education and homeroom guidance in the Philippines, and religious education in Indonesia. Second, while the Philippines and Indonesia implement mental health education based on established policies, Japan lacks a core mental health literacy policy but has developed and implemented related curricula through its course of study guidelines. This study revealed the partial implementation of mental health literacy education in the Philippines, Indonesia, and Japan. The Philippines offers a nearly comprehensive curriculum on mental health literacy (grades 1–12), Japan incorporates it into health education (grades 5–10), and Indonesia integrates it into religious education (grades 1–12). While the Philippines and Indonesia align with mental health policies, Japan relies on its national curriculum without a core policy. A key challenge was indicated involving teachers, guidance counselors, or school health personnel as key actors to support students with mental disorders or those potentially at risk, as well as to handle emergency cases of mental disorders in schools. Recommendations include systematic monitoring of the implementation of school-based mental health policies, collaboration with UN agencies to align with international standards while incorporating culturally tailored strategies for each country.