Objective: To understand the role of family adversity in the onset and desistance of sibling victimization, we examined school-age children’s sibling victimization patterns using 2 waves of longitudinal data from a nationally representative sample. Method: Parents of children aged 5–9 and children aged 10–12 years old (N = 945, Mage = 8.5 years, 52% male) participated in 2 waves of telephone interviews, 2 years apart. Results: We compared family adversity for children whose victimization by a sibling emerges at Wave 2 (the New group) versus those children who do not experience any sibling victimization at either Wave (the None group). Also, we compared children who continue to be victimized (the Persist group) versus those children for whom victimization stops (the Desist group). An increase in family adversity was associated with initiation of sibling victimization, and termination was related to a decline in family adversity. These patterns applied more to girls than boys. Conclusions: Family adversity was associated with the onset and termination of sibling victimization. In adverse family conditions, girls may be particularly vulnerable to sibling victimization. For families dealing with loss, illness and other transitions, parents and children may need help preventing and interrupting sibling victimization. (PsycINFO Database Record (c) 2016 APA, all rights reserved)