Schools are the primary environment in which to conduct prevention programs for school-age children. Educators, policy makers, and psychologist argue that prevention efforts should begin as early as possible to maximize their effectiveness. Surprisingly, there are relatively few school-based prevention programs targeted for preschoolers. Given the evidence supporting earlier rather than later prevention efforts and the fact that many children in the United States attend preschool programs, more research on the feasibility and effectiveness of prevention programs administered in preschool environments is warranted. In this article, we review the existing literature on school-based prevention programs targeted for preschool children. We examine whether school-based prevention programs are theory driven, developmentally appropriate, culturally sensitive, and aimed specifically at symptom reduction or behavior promotion. Based on the findings of this review, our aim is to identify gaps in the prevention research literature regarding programs for preschoolers and propose research to address such gaps to create more effective school-based prevention programs for young children.