Extensive prior research has examined the effect of low self-control on delinquency, as well as whether this effect is moderated by criminal opportunity. The purpose of our study is to examine whether these relationships can be extended to cyberbullying as an outcome. In doing so, we discuss ways in which key theoretical arguments and common measurement strategies must be modified in order to apply to cyberbullying. Using data from a nationally representative sample of South Korean youth, the analysis reveals that low self-control is, indeed, a significant predictor of cyberbullying. Moreover, we find that the effect of low self-control on cyberbullying is amplified by criminal opportunity, but only when opportunity is measured in a manner that specifically refers to the usage of social media. In contrast, opportunity as traditionally measured has no moderating effect. We suggest several avenues for future research, and conclude that studies of cybercrime must pay careful attention to conceptualizing and operationalizing key concepts with specific regard to the differences between cybercrime and traditional forms of offending.