Rates of social, emotional, and behavioral difficulties are rising and significantly impact K-12 students' learning. Unfortunately, many teachers report being underprepared to identify, refer, or manage these symptoms. This study utilized a graduate course to address the mental health literacy needs of in-service teachers. Significant improvements in mental health literacy were achieved at course completion. Several participants also reported examples of how they demonstrated mental health literacy in their subsequent educational practices. These findings support the impact of in-service teacher education that focuses on mental health literacy.