Expanded school mental health (ESMH) programs are critical for addressing children's social and emotional development in schools. As broad, multisystem approaches, ESMH programs rely on teachers for effective and sustainable primary, secondary, and tertiary school mental health service delivery. In light of the increasing mental health needs among children, an improved understanding of specific ways in which teachers are affected by school mental health approaches can lead to improved implementation of such services. This is especially important considering existing evidence that teachers' ability to implement student support strategies is influenced by several other factors, including teacher stress. In light of this, this study investigated teachers' perceptions of student mental health needs, student support systems, and teacher stress. Results revealed that different aspects of student mental health needs and perceptions of student support systems predicted teachers' perceptions of stress. The article concludes with a discussion of the findings' implications for the development, dissemination, and implementation of strategies designed to address student mental health needs.