This study examined the relationship between teachers’ readiness in mental health capacity building and the mental health literacy of senior high school students. Utilizing a quantitative research design, the study involved 83 senior high school teachers and 342 student-respondents from selected institutions. Teachers’ readiness was assessed across four domains: mental health awareness, early identification, intervention strategies, and self-care practices. Meanwhile, students’ mental health literacy was evaluated in terms of beliefs, knowledge of mental health problems, first aid skills and help-seeking behaviors, and self-help strategies. Findings revealed that teachers demonstrated a generally very high level of readiness in all domains of mental health capacity building, with grand means ranging from 4.28 to 4.59, interpreted as “Very Much Ready.” Among the domains, self-care practices obtained the highest mean, indicating strong recognition among teachers of the importance of maintaining their own mental well-being. Teachers also showed strong readiness in fostering supportive environments, collaborating with mental health professionals, and referring students to appropriate services, although slightly lower ratings were observed in areas related to communication and application of specific intervention strategies. Correlation analysis showed significant positive relationships between teachers’ readiness and students’ mental health literacy. Specifically, all four domains of teachers’ readiness were significantly correlated with students’ beliefs about mental health, knowledge of mental health problems, and use of self-help strategies. These findings suggest that higher levels of teacher preparedness contribute to more positive mental health perceptions, improved knowledge, and increased use of coping strategies among students. Overall, the study highlights the critical role of teachers as frontliners in promoting mental health within schools. Enhancing teachers’ competencies in mental health capacity building can significantly influence students’ mental health literacy and well-being. The results underscore the need for continuous professional development programs to further strengthen teachers’ skills in communication, early identification, and intervention practices.