Background: Universal, classroom-based mental health literacy (MHL) curricula are associated with improved mental health knowledge, attitudes, and help-seeking behaviors. Young adolescents are an ideal target given their need for and receptivity toward MHL education. Methods: We conducted a scoping review to identify universal, school-based MHL programs primarily for students aged 10-14 years, with adequate descriptions of curriculum implementation and content, and measured outcomes. Findings: Thirty-one articles describing 24 programs met the inclusion criteria. The content and educational strategies varied, with no two programs having the same curriculum. The studies show promising results for improvement in mental health knowledge, attitudes, help-seeking, and student mental health. Implications for School Health Policy, Practice, and Equity: Collaborative work between educational and mental health professionals, along with rigorous study of outcomes, aiming to reach a consensus on a core MHL curriculum and best implementation practices, will advance efforts to improve MHL. Conclusions: This scoping review confirmed that existing universal, school-based MHL programs for middle school-aged students improve mental health knowledge. The programs are diverse, and their outcomes are often challenging to compare. Ongoing study in this field to optimize design and implementation for improved effectiveness is needed.