Academic self-efficacy is an important condition to ensure learning effectiveness and improve the sustainability of online learning quality. The present study intended to examine the relationship among online teacher support, academic procrastination, and academic self-efficacy by employing a questionnaire survey and structural equation modeling in the online learning environment. We report on survey data from N = 827 college students from China. The results showed the following: that online teacher support and its emotional, cognitive, and autonomy support dimensions have significant positive effects on academic self-efficacy, and it can predict the academic self-efficacy of college students through the mediating effect of academic procrastination. Therefore, in order to enhance the academic self-efficacy of online learners, it is crucial to increase online teacher support, provide guidance and motivation to online learners, reduce academic procrastination, and improve the emotional, cognitive, and autonomy support perceived by students in online courses and learning activities. The findings contribute to the exploration of the impact and mechanism of online teacher support regarding the academic self-efficacy of learners, providing theoretical and empirical support for enhancing academic self-efficacy in online learning and the development of a sustainable quality of teaching.