This study focuses on the relationship between reinforcement sensitivity and aggression according to the combination of forms and functions of aggression (i.e. proactive overt, proactive relational, reactive overt and reactive relational), and on the moderating role of gender in this relationship. The survey included 656 adolescents (55.33% male) from the city of Zagreb, Croatia. The results show that reward sensitivity has the highest relation with proactive overt aggression, while punishment sensitivity has the highest relation with reactive relational aggression. A moderator analysis shows that boys with high reward sensitivity manifest higher level of proactive overt aggression than girls with high reward sensitivity. Also, boys with high punishment sensitivity manifest higher level of reactive relational aggression than girls with high punishment sensitivity. The findings can help to improve the treatment of aggressive behaviour in adolescence by focusing on reward sensitivity in relation to punishment sensitivity.