The purpose of this study is to explore how integrating Keller’s ARCS model into an online discussion forum can enhance student-teacher and student-student interactions. Specifically, three case studies are analyzed and elaborated to test and verify their effectiveness. The first case uses the non-participating observer to make observation, and the result reveals that the ARCS model did enhance interactions between the teacher and students. The second case adopts the survey method, and the result shows that the ARCS model did increase the number of articles in the online discussion forum. The third case also adopts the survey method, and the result shows that the ARCS model did increase the number of articles in the online discussion forum and students’ willingness to share. In sum, Keller’s ARCS model did enhance student-teacher and student-student interactions. Finally, practical suggestions and future directions are addressed