Child sexual abuse (CSA) is a worldwide social problem which has received much attention from policy makers, researchers, and practitioners. A considerable portion of CSA research has focused on adult offenders, the result of which is that most of our existing knowledge regarding prevention and intervention has been based on abuse perpetrated by this population. The current literature review, by contrast, was designed to spotlight the phenomenon of preadolescent peer sexual abuse (PAPSA), focusing on children ages 12 and under, using Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The results revealed scant empirical data, with only nine studies focusing on this phenomenon. As the basis of their investigations, most of the reviewed studies used definitions of sexual harassment among peers, rather than definitions of more severe forms of sexual abuse, and showed conflicting results depending on the ages and genders of the peers involved. In addition, prevention programs for peer sexual abuse/harassment were not targeted toward preadolescents. Additional findings indicated a lack of empirical knowledge with respect to core aspects such as victims’ personal characteristics and subjective experience, the dynamic of the abuse, and the disclosure process. This systematic literature review emphasizes the need for an in-depth and thorough conceptualization and empirical examination of the PAPSA phenomenon and its unique characteristics.