Dark personality traits (i.e., Machiavellianism, psychopathy, narcissism, spitefulness, and sadism) are associated with adverse childhood experiences and deviant online behaviors. However, their mediating role between childhood emotional abuse and cyberbullying has never previously been investigated. We examined direct and indirect associations of childhood emotional abuse and cyberbullying via dark personality traits among 772 participants. Men were better characterized by dark personality traits and were more likely to engage in cyberbullying than women, and there were no sex differences in childhood emotional abuse. Collectively, dark traits fully mediated the relationship between childhood emotional abuse and cyberbullying in men, with partial mediation in the total sample and women. More specifically, Machiavellianism and spitefulness were mediators in both samples, sadism was a mediator in men and the total sample, and psychopathy was a mediator in the total sample and women. The dark personality traits can account for the association between childhood emotional abuse and cyberbullying, especially among men.