The paper assessed social media obsession and associated deviant behaviour among youths in contemporary Nigerian society. Four research questions and corresponding hypotheses were answered and tested in the study. Survey research design was adopted in the study while the population comprised youths in Yenagoa Local Government Area out of which 383 youths were sampled using convenience sampling technique. The instrument used for data collection was a 15- item questionnaire titled “Social Media Obsession and Deviant Behaviour among Youths Questionnaire”. The questionnaire was validated by three Sociology of Education experts at University of Port Harcourt. The reliability was estimated using Cronbach Alpha Statistics and a coefficient of 0.89 was obtained. Three hundred and eighty-three copies of the questionnaire were administered out of which 372 copies (174 males and 198 females) representing 97.1% were retrieved. The research questions were answered using mean, standard deviation and logistic regression while the hypotheses were tested using z-test at 0.05 level of significance. The result of the study indicated that social media was basically used for business purpose, academic purpose and building of interpersonal relationships among the youths. The findings revealed that the deviant social media behaviour exhibited by the youths included sexting, cyberbullying, internet fraud among others. The study also revealed that ownership of social media contributed to deviant behaviour among the youths. The study showed that counselling and formulation of appropriate policies can be used to assist youths to use social media responsibly. It was recommended that counselling services should be provided for youths on how to improve their use of social media sites.