Cyber-bullying (CB) is a prevailing phenomenon among University students, but scarcely investigated, thus leaving its correlates largely unexplored. Recently, integrated theoretical models were proposed for the explanation of the phenomenon, investigating complex interactions between personal and contextual factors. The present study was purported to investigate the association between several individual and contextual variables (attachment, Big Five personality traits, Internet use frequency, problematic Internet use, οnline disinhibition, loneliness, psychopathology) and CB/Cyber-victimization (CV) among 175 Greek University undergraduates, based on the General Aggression Model. Results showed that participants who used the Internet more frequently scored higher in CB. Significant positive correlations were observed between both CB and CV with Neuroticism, loneliness, anxiety, hostility, online disinhibition, and Problematic Internet Use, and positive with Agreeableness. Furthermore, CB was negatively correlated with Conscientiousness and CV negatively with depression. CB was predicted by low Agreeableness, frequent Internet use and higher levels of negative outcomes when using the Internet, while CV was predicted by low Agreeableness, high Extraversion, high loneliness and high compulsive Internet use. Overall, findings of this study indicate that CB and CV may involve students who make problematic Internet use, have specific personality traits and face various social difficulties and psychopathological symptoms.