While test anxiety is a problem in asynchronous online courses, few studies have systematically investigated learning factors influencing test anxiety in asynchronous online courses. Additionally, emotional engagement has been identified as a mediator between learning factors and test anxiety. Therefore, this study clarified the mediating role of emotional engagement between learning factors (i.e., self-efficacy, instructor-learner interaction, learner-learner interaction, perceived ease-of-use, and perceived usefulness) and test anxiety in college-level asynchronous online courses. Overall, 316 college students participated in this study. Structural equation modeling analysis examined the relationships between learning factors and test anxiety. Self-efficacy, instructor-learner interaction, and perceived ease of use had direct and significant negative influences on test anxiety. Self-efficacy, instructor-learner interaction, learner-learner interaction and perceived usefulness had indirect negative effects on test anxiety mediated by emotional engagement. The current findings indicated that instructors should consider self-efficacy, instructor-learner interaction, learner-learner interaction, perceived ease of use, and perceived usefulness when designing and conducting asynchronous online courses to reduce college students' test anxiety.