Moral disengagement is a cognitive mechanism that seeks to avoid the feeling of guilt in the face of transgressive behaviors and seems to be present in behaviors such as cyberbullying, cybergossip or bullying in adolescence. Few studies have explored this connection in the primary school years, even though gossip, bullying and cyberbullying are also frequent during these early years. The aim of this study was to examine, in primary school children, the relationship of aggression in bullying, cyberbullying, and cybergossip with moral disengagement, over a time interval of 18 months. The longitudinal study was conducted through different questionnaires with a final sample consisting of 507 schoolchildren (48.5% girls; M = 11.86; SD = 0.74). The results showed that there was a direct, significant relationship between involvement as an aggressor in cyberbullying behaviors and moral disengagement, but this relationship was not significant in aggressive behaviors in bullying and cybergossip. These results are discussed in relation to the importance of the formation of moral judgment during these years and its educational implications.