Insufficient attention has been given to the integration of the mediating effect of Internet gaming disorder (IGD) symptoms on loneliness and four components of aggression-physical aggression, verbal aggression, anger, and hostility-in the Malaysian context. In the present study, 410 participants with (a) at least 1 year of Internet gaming experience and (b) between ages 20- to 39 years were recruited using the probability proportional to size sampling method. Participants were undergraduate students and working adults. Self-reported questionnaires (the Internet Gaming Disorder Scale, University of California, Los Angeles Loneliness Scale, and the Buss-Perry Aggression Questionnaire) were used. The present study found that loneliness positively predicted four components of aggression (i.e., anger, hostility, physical aggression, and verbal aggression) and symptoms of IGD. Relationships between loneliness and the four components of aggression were partially mediated by IGD symptoms. The present study enriches and consolidates existing empirical evidence, particularly in the Malaysian context. If the mediating effect is not emphasized, it may lead to spurious conclusions that can significantly diminish the effectiveness of interventions that are meant to manage aggression.