The mental well-being of individuals is as important as their physical health, contributing to their overall quality of life. It is, however, often neglected due to associated stigma, with people silently suffering from mental health challenges. In India, a large population is struggling with mental health concerns, especially teenagers and adolescents. With a population of around 1.4 billion, India faces an immense shortage of adequate mental health services, realizing the need for alternate strategies to fill the treatment gap. As teachers spend much time with students in school, they can contribute to their mental well-being if provided with capacity-building opportunities. This study aims to measure the impact of a teacher sensitization program in Indian government schools on mental health-related knowledge, beliefs, and the behaviours demonstrated by them in the classroom while interacting with children, creating a ripple effect towards students’ mental well-being. A total of 136 teachers who were teaching at government high schools in the district of Varanasi, Uttar Pradesh, India, were included in the study. The study used a pre- and post-design to investigate the impact of a teacher sensitization program on their understanding related to mental health. The results indicated notable improvements in teachers' attitudes and beliefs toward mental well-being, with significant improvements observed in areas such as behaviour, teachers' body language, relationships with students, and the use of effective teaching strategies. The findings highlight the importance of professional development initiatives to equip teachers with the skills to effectively support student well-being.