Online learning is rapidly expanding across the educational landscape, particularly at the tertiary level of education. When combined with appropriate pedagogy, the tremendous advancement of technology has transformed the face of education. This integration has created new possibilities for enhancing teaching quality. Augmented Reality (AR) is one of the recent technologies to help make learning interactive and engaging. The broad adoption of AR on mobile devices is related to the enormous use of mobile devices globally. Thus, this paper reviews several works of literature on mobile AR and demonstrates its educational potential. After identifying the empirical studies of AR, this review highlights its potential in terms of learner outcomes, interaction, motivation, visualization, and collaboration, and its challenges, particularly in the English as a foreign language (EFL) context. Further research also needs to investigate diverse mobile AR apps for more engaging virtual online courses.