We examined the moderating effect of gender on witnessing bullying, defending, and internalizing symptoms among sixth-grade students at one middle school in the northwestern United States. Results indicated that for females, witnessing bullying was positively associated with depressive symptoms and social anxiety, whereas for males, defending was positively associated with depressive symptoms. Findings suggest the importance of equipping female students with strategies to cope with witnessing bullying and providing male students with appropriate intervention skills for defending targets.