The present study aimed to explore the relationship between cyber-bullying and psychological security, psychological loneliness, and age. In other words, it sought to identify the predictive power of these three variables on cyber-bullying among university students. Participants were 426 male and female Saudi university students aged between 18 and 36 years (M = 21.00, SD = 2.42). Three scales were used to probe cyber-bullying and psychological security and loneliness. Data analysis revealed that 17.6% of the participants were cyber-bullies. Significant differences in cyber-bullying were found by gender (in favor of males). A significant positive correlation was found between cyber-bullying on one hand and psychological security and loneliness and age on the other. The findings also revealed that cyber-bullying among university students can be predicted by psychological loneliness and age. Psychological loneliness is the best predictor of cyber-bullying. It explained .284 of cyber-bullying, while age, psychological loneliness explained .339 of cyber-bullying. These findings shed more light on the psychological aspects included in cyber-bullying. It is a significant contribution in that it identified the motives beyond cyber-bullying and its adverse effects on individuals.