Mental health challenges (including mood, anxiety, and behavioral disorders) affect up to one-fifth of adolescents ages 13–18. Although these disorders are associated with impairments in psychological, academic, social, and family domains, they are often left untreated. Schools have great potential to address this service-underutilization gap by identifying those students at risk through mental health screening tools and by providing treatment at no cost for students. However, at the secondary level, school personnel partly expect high school students to initiate support for themselves. The present study advances research by exploring the variables related to adolescent mental health help-seeking intentions within the school setting. Specifically, this study assesses the utility of the theory of planned behavior in an effort to identify what factors relate to high school students' willingness to seek help at school. A secondary aim of this study was to examine why adolescent boys are consistently less willing to seek help for mental health problems than adolescent girls. Results of this study highlight important factors to target when developing interventions to increase help-seeking intent in high school students.