This article draws on moral theory to advance digital citizenship education and explore how adolescents aged 13-16 make decisions when confronted with incivility, such as cyberbullying, on social media. Given the extent to which digital citizenship education may be approached in line with deontological (rules), utilitarian (consequences) and/or virtue ethical (character) theories, we argue that it is important to know which of these underpin adolescents' moral decision making online. To address this question, this article reports findings from a survey completed by 1947 13-16 year olds in England. Chi-square tests, binary logistic regressions and other exploratory analysis showed that most 13-16 year-olds use virtue ethical reasons to justify moral actions. We conclude that if online incivility is to be reduced, policymakers, educators and parents should focus more on virtue- and character-based approaches to digital citizenship education.