<p>The prevalence of online learning has been on the rise around the world. The present study aimed to examine the complex relationship between social anxiety, fear of missing out, academic procrastination, and online learning engagement among 1006 students at B University. Utilizing a sequential explanatory mixed-method approach, we first collected quantitative data via questionnaires and analyzed data using structural equation modeling, and then conducted interviews with 16 students to contextualize and deepen the understanding of the quantitative results. The results unveiled that social anxiety, academic procrastination, and fear of missing out exhibited negative associations with online learning engagement. Academic procrastination mediated the effect of social anxiety and fear of missing out on online learning engagement. By identifying the effects of social anxiety, fear of missing out, and academic procrastination, this study develops targeted interventions for educators to enhance online learning engagement.</p>