This study examined social media usage among undergraduates vis-à-vis its influence on their studies. The study adopted a descriptive survey research design. The population for the study comprised all undergraduate students of Obafemi Awolowo University, Ile-Ife Nigeria. Five faculties were randomly selected, from which 850 students were selected using random and convenience sampling techniques. A self-designed instrument titled "Social Media Usage and Influence Questionnaire (SMUI-Q)" was used for data collection. The results show social media platforms used by undergraduates, include WhatsApp (97%), Facebook (85%), Instagram (65%), YouTube (62%), Twitter (25%), LinkedIn (21%), Google Plus (15%), Snapchat (10%), and Skype (7%). Further, undergraduates spend an average of 2-3 hours daily on social media, and their perceived purposes of social media usage include: socialisation (83%), information (74%), academic (73%), business (68%), and entertainment (61%). The results highlight Internet addiction (45%), distraction (32%), anti-social behaviour (6%), cyber bullying (4%), and writing and spelling skills deficiency (24%) as the influences of social media on undergraduate studies. The study concludes that the social media platforms mostly used are WhatsApp, Facebook, Instagram, and YouTube; which are used mainly for socialisation, information, and academic purposes and may also perhaps suggest the reason for addiction to social media.