This study aims to investigate the effects of competition through a digital leaderboard in gamified online discussions on learners' behavioral and cognitive engagement in learning. Twenty-three graduate students pursuing master's degree in instructional technology in a public university in Indonesia were involved in a five-week quasi-experiment (N = 23; Group A = 12 & Group B = 11). All discussion activities were performed on a gamification platform designed specifically to facilitate online discussions. Several game elements were used on this platform, including points, badges, quizzes, and leaderboards. The discussion topics encompassed instructional design case studies in varied contexts (K-12, higher education, and industry). In this study, we measured behavioral engagement by tallying the number of posts and earned points from participants. Additionally, cognitive engagement was evaluated by analyzing the cognitive level evident in participants' posts. A framework entitled the levels of Knowledge construction was used for analyzing the quality of the posts. After a five-week implementation period, our investigation revealed that incorporating competition through leaderboards did not yield significant differences in learners' behavioral engagement, measured by two metrics: the number of posts (Z = - 0.346, p = 0.729) and earned points (Z = -1.283, p = 0.200). Regarding cognitive engagement in online asynchronous discussions, no evidence supported the effectiveness of competition in gamified online discussions across various levels of knowledge construction, including initiation (Z = -1.826, p = 0.068), development (Z = -1.604, p = 0.109), and construction (Z = -1.289, p = 0.197). This study also scrutinized limitations and critical issues, offering essential recommendations to guide future research.