The study investigated social media usage and antisocial behaviours (cultism and bullying) among secondary school students in Eleme Local Government Area of Rivers State, Southern Nigeria. A sample of 400 students from a population of 5233 was used for the study. Taro Yamen’s formula and simple random sampling were used to compose the sample. Three research questions were answered while three corresponding null hypotheses were tested at 0.05 level of significance. Two instruments titled Anti-social Behaviour Scale (ABS) and Social Media questionnaire (SMQ) were used for data collection. The instruments were validated by experts in Measurement and Evaluation. The reliability of the instruments was estimated using Cronbach alpha reliability method of internal consistency. Data were analyzed using multiple regression, analysis of variance (ANOVA), simple regression and t-test associated with regression. Findings revealed among others that social media usage (Facebook, WhatsApp and Instagram independently accounts for 63.5% variation in tendency to cultism activities among secondary school students of Eleme Local Government Area of Rivers State, Southern Nigeria. It was also revealed that social media usage (Facebook, WhatsApp and Instagram) accounts for 44.65% variation in tendency towards bullying among these students. Based on the findings, it was recommended among others that students should be taught on how to make more constructive and fruitful use of their phones. The implication of the results was highlighted in line with the findings. The study successfully contributed to knowledge as it has established empirically that students can learn the acts of cultism from their use of social media.
