Background: Universities and institutes of higher education are always regarded as centers for thinking and disseminating sciences. To improve the scientific quality of such centers, direct their intellectual, religious, and political movements, and ensure that they fulfill their responsibilities and maintain their dynamism, the programs pursued by such centers should undergo constant quality assurance. The major objectives of e-learning are reducing costs, increasing accessibility, and improving quality. The concept of quality, however, is still a challenging issue in electronic and virtual courses and requires lots of research. Despite numerous assessments of e-learning from different perspectives, many experts believe that no comprehensive study has focused on e-learning quality assessment. Thus, the current study was an attempt to conduct a systematic and scientific research with the aim of offering scientific and executive suggestions for improving quality assurance in e-learning in those centers that are implementing or have offered to implement this type of learning. Method: This study adopted a comparative approach by studying papers through case-review. Then, the factors related to quality assurance were extracted, coded, summarized, and combined. Subsequently, using case analysis table, the main factors for e-learning quality assurance were identified. Results: Overall, 27 factors that are related to e-learning were identified and were subsequently reduced to nine factors using case analysis table and summarization and categorization of factors with similar themes. Conclusion: Establishing a proper structure to assess quality is one of the main factors leading to success in assuring quality in higher education. To this end, a suitable organizational structure should be created to assess and improve e-learning educational system. In this study we aimed to identify the main factors influencing e-learning quality assurance. At the end, nine factors were identified.