In the current prospective study, we investigated (1) whether high and low BMI in early childhood puts a child at risk of victimization by their peers, and (2) whether being victimized increases BMI over the short‐ and long‐term, independent of the effect of BMI on victimization. We also examined whether gender moderated these prospective associations. Participants were 1,344 children who were assessed yearly from ages 3 to 10 years as part of the Québec Longitudinal Study of Child Development (QLSCD). BMI predicted annual increases in victimization for girls aged 6 years and over; for boys aged 7 and 8 years of age, higher BMI reduced victimization over the school year. Further, victimization predicted annual increases in BMI for girls after age 6 years. When these short‐term effects were held constant, victimization was also shown to have a three and 5‐year influence on annual BMI changes for girls from age 3 years. These short‐ and long‐term cross‐lagged effects were evident when the effects of family adversity were controlled. The findings support those from previous prospective research showing a link between higher BMI and victimization, but only for girls. Further, being victimized increased the likelihood that girls would put on weight over time, which then increased future victimization. The implications of these prospective findings for interventions are considered. Aggr. Behav. 9999:XX–XX, 2015. © 2015 Wiley Periodicals, Inc.