In this study we examined children's self-efficacy, outcome expectations, and outcome values in relation to bystander responses in bullying situations. We proposed that beyond the effect of self-efficacy, the decision to defend the victim of bullying vs. remain passive vs. reinforce the bully depends on outcomes children expect from defending, and on the value they place on these outcomes. Our sample consisted of 6397 Finnish children (3232 girls and 3165 boys) from third, fourth, and fifth grades (mean ages 911 years). Results showed that the motivational underpinnings of defending the victim, remaining passive, and reinforcing the bully varied. Defending was associated with the expectation that the victim feels better as a result of defending as well as valuing such an outcome. Reinforcement of bullying was associated with negative expectations and not caring about the positive outcomes. Conflicting expectations and values were linked to remaining passive. Results are discussed in terms of their implications for anti-bullying interventions.