This study uses self-determination theory to examine the effect of gamification on the students' behavioral, emotional, and cognitive engagement in online discussion forums by providing more instructor badges than automatic badges and using a quasi-experimental one-group pretest-posttest design. Behavioral engagement was measured using the number of posts and replies; emotional engagement was measured using perceived relatedness; and cogitative engagement was measured by the quality of the post/reply's content. Sixty participants used the developed online discussion website and held two 3-day discussion sessions (non-gamified and gamified) with different topics. The data were collected using user logs (number of posts and replies), questionnaire responses (perceived relatedness), and assessment rubrics (scores on the post/reply content), analyzed using the one-way repeated measures analysis of variance. The results revealed that gamification affected emotional engagement, which was influenced by the "like" feature, which made it easier for participants to appreciate others' activities. However, this feature also decreased the number of replies (behavioral engagement) because the students perceived "liking" as an easier way to appreciate other posts/replies instead of writing a reply. The number of posts also decreased since participants' motivation in the second session tended to focus on the quality of the content caused by the badge list page, which guides the expected best content from the participant. This study can provide guidance to universities in implementing gamification in LMS.