This study examined the relationship of positive and negative beliefs about competition and social comparison orientations with second language (L2) learners' engagement and performance. The participants were 343 Iranian undergraduate students, including 69 (20.1%) male and 273 (79.9%) female learners. They responded to self-report scales on beliefs about competition, cooperative and competitive orientations, and engagement. The results of structural equation modeling showed that all types of engagement (emotional, behavioral, agentic, and cognitive) were significantly and positively predicted by cooperative orientation and negatively predicted by negative beliefs about competition. Moreover, the results indicated that positive beliefs about competition did not predict any type of engagement and competitive orientation negatively predicted language performance. These findings highlight the importance for language instructors to consider the competitive and collaborative dynamics within their classrooms. By fostering cooperative environments, educators can enhance student engagement in second language acquisition (SLA), ultimately leading to improved learning outcomes. This research suggests that a balanced approach to competition and collaboration is essential for optimizing language learning experience.