A great deal of research has investigated weight as a predictor for bullying victimization. However, weight is rarely examined in light of its potential role in explaining bullying perpetration, despite the fact that the definition of bullying typically requires a power imbalance, which can refer to either social power or physical size. Using negative binomial regressions, we investigated weight as a predictor of overt and relational bullying behaviors for a sample of 3208 6th–8th graders from 11 schools in a northeastern state. We examined whether this relationship differs by gender, and we explored whether objective size or perception of size is more predictive of perpetration. We also examined whether certain protective factors, like a positive school environment, moderated the effect of weight on bullying perpetration. We found that students who reported a higher BMI engaged in more overt, but not relational, bullying perpetration. Interestingly, students with misperceptions about their weight reported higher levels of both types of bullying perpetration, while students reporting a more positive school climate engaged in less overt and relational bullying. We also found gender differences in that girls are statistically more likely to commit overt bullying if they have a higher BMI. Our results suggest that prevention programs should address weight as a predictor of bullying behaviors, especially for girls, but also that body image and misperception of weight are important topics for prevention programs.