Despite the fact that bullying has been consistently linked to moral disengagement among schoolchildren, research that distinguishes among the four loci of moral disengagement (cognitive restructuring, minimizing one's agentive role, distorting consequences, and victim attribution) to better understand bullying is scarce. The aim of this longitudinal study, conducted in Sweden, was to explore in both female and male students whether the four loci of moral disengagement are concurrently associated with bullying when students are around age 12 and then again around age 14, and whether the four loci of moral disengagement in age 12 predict bullying at age 14. The current paper is based on data from 1,053 students who completed a questionnaire both in sixth and then, two years later, in eighth grade to collect self-reported data on moral disengagement, traditional school bullying perpetration, sex and age. According to the findings, concurrent associations between moral disengagement loci and bullying vary across age and sex, but cognitive restructuring was consistently related to bullying in all conditions. Cognitive restructuring was the only moral disengagement locus from grade six that significantly predicted bullying in grade eight, but not when controlling for bullying in grade six. The results indicate the need to individualize intervention actions to address moral disengagement in terms of sex and age.