A growing number of researchers have begun to highlight the potential negative effects of the excessive use of social media on college students. In particular, college students engage in social media multitasking, in which they perform multiple tasks simultaneously. Such action could adversely influence their academic performance. Hence, on the basis of the situation-organism-behavior-consequence paradigm, we developed a research model to explore the etiology of social media multitasking and its impact on college students' academic performance. Using partial least squares--structural equation modeling techniques to analyze the survey data of 523 Chinese college students, we found that the fear of missing out (the situation) is positively associated with social media multitasking (the organism), which in turn is positively related to cognitive distraction (the behavior) and ultimately leads to a decline in academic performance (the consequence). Our study deepens the understanding of the phenomenon of social media multitasking among college students and can provide a reference for educators to implement intervention measures.