Society's awareness of sibling violence and sexual abuse, and its response, has lagged behind other child abuse issues and concerns. In comparison with parentchild abuse, sibling abuse is generally underreported by parents, teachers, mental health professionals, and communities. Child welfare services and the legal system are more reluctant to accept and respond to reports of sibling violence and sexual abuse, and researchers agree that it has received less attention than other forms of child maltreatment despite good evidence that suggests it is more common and no less injurious than child abuse when a parent or other adult is the perpetrator. This chapter describes the historical context of sibling violence and sexual abuse, factors and methods essential in its identification and assessment, definitions of sibling physical violence (SPV), sibling psychological maltreatment (SPM), and sibling sexual abuse (SSA), its prevalence and relationship to other forms of peer and family violence, as well as individual, family, and ecological risk and protective factors. Cultural, ethnic, and gender considerations are discussed as well as an overview of clinical research on sibling abuse and its harmful effects. Evidence-based treatment strategies and clinical case material are utilized to illustrate fundamentals of a therapeutic approach to child and family intervention guided by trauma-informed principles. The current state of research and practice, future directions, and recommendations for policy and prevention are also summarized.