Siblings play an important role on child development and personality. However, several characteristics of the sibling relationship put sibling interactions at risk for frequent incidents of conflict. Several studies report that violence among siblings may be the most common form of family violence, with prevalence rates remaining relatively constant over the past 40 years, but society and people in the family environment still often overlook it, deeming these aggressive interactions 'normal'. Society recognizes child abuse, intimate partner violence, and elder abuse as significant social problems, but awareness of sibling abuse as a serious form of family violence remains low. The aim of the present chapter is to contribute to a better understanding of non-lethal physical abuse of siblings. The chapter will explore: differences between play fighting and sibling violence; differences between rivalry and sibling violence; associations of sibling violence with other forms of domestic violence (parent-to-child violence, dating violence, parent-to-parent violence, bullying at school); prevalence of different types of sibling violence (e.g., physical, verbal, and sexual); and perceptions of sibling violence from victims, perpetrators, and the wider society. The chapter will also explore risk factors for sibling violence (e.g., peer bullying, hostility, and anger), alongside short-term and long-term consequences (e.g., mental health difficulties, increased aggressive behavior outside the home, and interpersonal problems) of these behaviors. The role of other variables such gender, age, family communication, parenting quality, sibling attachment, and differential treatment by parents in sibling violence will also be considered. Cultural differences will be explored. The literature will be discussed in relation to several theoretical perspectives, such as family systems theory, social learning theory, and feminist theory, to help understand sibling violence. Suggestions regarding prevention and intervention are also discussed.