In today's society, social media have become an almost indispensable part of daily life, particularly among university students, who are generally heavy social media users. Social media multitasking has also been increasingly prevalent. Little, however, is known about how social media usage and social media multitasking influence the academic performance of university students. This study examined whether and how these two behaviors predict academic performance among university students. From a sample of 348 undergraduate students at a comprehensive university in Hong Kong, this study found that using social media for academic purposes was not a significant predictor of academic performance as measured by cumulative grade point average, whereas using social media for nonacademic purposes (video gaming in particular) and social media multitasking significantly negatively predicted academic performance. © 2016 Elsevier Ltd. All rights reserved.