This study aimed to investigate end-of-course achievements, cognitive levels of the preservice teachers' posts, interaction types and their perceptions about asynchronous online discussions. In this mixed method research study, 72 pre-service teachers were included adopting a convenience sampling method. Moreover, 10 volunteering pre-service teachers were selected for the interviews according to maximum variation sampling method. The data were collected through an achievement test, students' Edmodo posts and semi-structured interviews, and analyzed through an ANCOVA analysis, chi-square test and thematic analysis. The results of the study showed that although the mean scores of experiment group was higher than the control group, being either in cased-based-discussion group or control group did not affect the curriculum knowledge of pre-service teachers significantly. Experiment group tended to make more posts than the control group; however, the difference was not significant. Finally, although pre-service teachers mostly mentioned affordances of asynchronous online discussions such as engaging learners, increasing peer interaction, obtaining feedback, having more time to think before posting responses, they also stated internal and external limiting factors to post in asynchronous online discussions which were discussed in detail.