The prevalence of cyberbullying cases has been increasing over the years and it causes detrimental effects on one's mental health and psychological well-being. This cross-sectional research aims to determine the significant relationship between proactive aggression, reactive aggression and self-esteem on cyberbullying among undergraduates in Malaysia. 255 participants were recruited through purposive sampling. Questionnaires were distributed online via social media platforms such as Facebook, Instagram, WhatsApp, and Twitter. Three validated and reliable self-report measures were used to gather responses for this including Reactive-Proactive Aggression Questionnaire (RPQ), Rosenberg Self-esteem Scale (RSES) and Cyberbullying Test (CT). RPQ consists of 23 items followed by RSES with 10 items and lastly, CT consists of 45 items. All measures yielded a high reliability ranging from .84 to .95. The present study has found that proactive and reactive aggressions have a significant positive relationship with cyberbullying perpetration. However, proactive aggression has a stronger relationship as compared to reactive ones. Those with high proactive aggressions tend to involve more in cyberbullying as compared to reactive aggression. Moreover, it also found a negative but non-significant relationship between self-esteem and cyberbullying perpetration among undergraduates in Malaysia. It shows that those with high self-esteem tend to be cyberbullying victims but not perpetrators due to their frequent usage of social media. This study implies that it could be useful to tackle those involved in proactive aggressions as compared to reactive aggression and those with high self-esteem. Healthy ways to channel proactive aggression in which perpetrator seeks reward or dominance should be identified rather than focusing on those who reacts aggressively to a threat or provocation.