The purpose of this study was to investigate the relationship between the Big Five personality traits and Machiavellianism on Malaysian and international university students. The sample population consisted of 755 students (352 international and 403 local students) that were selected through multi-phase clustering at a Malaysian university. The instruments used were the NEO Five-Factor Inventory (NEO FFI), Mack IV, and General Health Questionnaire (GHQ). Data was analysed by means of two-way ANOVA, correlation analysis, and regression analysis. The outcome of the two-way ANOVA showed that neuroticism, agreeableness, and overall mental health and its subscale were significantly different between male and female students. A strong correlation was found between mental health, neuroticism, and Machiavellianism in both groups. According to the regression analysis, neuroticism held the highest effect on students’ mental health in both groups.