There is much research studying bullying and bystanding behaviors during adolescence. Recently, research has focused on social variables in an attempt to prevent or discourage bullying and encourage defending behaviors. This dissertation attempts to merge this research with a sociocognitive perspective. Moral disengagement, a sociocognitive variable, may help researchers have a better understanding of why adolescents bully their peers. This dissertation studies the role of moral disengagement in predicting bullying and bystander behaviors in adolescents from the US and Sweden. Results and implications of these findings are also discussed.