(1) Background: To examine the relationship among just-world beliefs, self-control, and cyberaggression among college students. (2) Methods: A total of 1133 college students were surveyed using the just-world belief scale, self-control scale, and cyberaggression scale. (3) Results: The results showed that college students with low levels of belief in justice frequently showed cyberaggression; belief in a just world directly and negatively predicted cyberaggression, and indirectly predicted student cyberaggression through self-control; gender moderated the indirect effect of self-control on cyberaggression and the direct effect of belief in a just world on cyberaggression. (4) Conclusions: Belief in a just world significantly and negatively predicts cyberaggression; self-control has an indirect significant effect on cyberaggression; the direct effect of belief in a just world on cyberaggression and the mediating effect of self-control on this association are moderated by gender.