This study investigated the predictive role of religiosity and ethnocentrism on cyber-aggressive behaviour among undergraduates of three randomly selected Federal Universities in Southeast Nigeria. A total number of 1,011 undergraduates were randomly selected from the student population. They comprised 397 male (39.3%) and 614 female students (60.7%), with ages ranging from 16 to 40 years, a mean age of 22.7 years and a standard deviation of 2.89. Three self-report survey instruments, namely the Religious Affiliation Scale (RAS), the Ethnocentrism Scale (E.S.) and the Cyber-aggression Typology Questionnaire (CATQ) were utilised to collect data for the study. Multiple regression statistics was employed for data analysis using SPSS Statistics v25. The result showed that religiosity did not predict cyber-aggression among undergraduates (β =.27, P ˃.05). However, ethnocentrism predicted cyber-aggression among undergraduates (β =.28, P<.01). It was recommended that activities such as creating awareness that promote attitude change, negate social loafing, and reduce the perpetration of cyber-aggression is necessary.