Decades of research on the impact of early mental health challenges in young children suggest that the effects are detrimental on children’s development without the presence of protective factors. As a factor for promoting mental health, early childhood classrooms and educators create optimal opportunities to identify and respond to children’s mental health concerns. However, little research explores the knowledge and skills of ECEs to effectively promote and support mental health challenges. The present study aimed to identify the mental health promotional knowledge, practices and experiences of ECEs in their preschool classrooms, as well as contribute to mental health promotion. Findings indicate that ECEs have little knowledge in promoting and supporting mental health in their classrooms and how that influences their practice. Suggestions for policymakers, early childhood practitioners, and future research are provided.