<p>Academic achievement in higher education is shaped not only by cognitive ability but also by social and emotional factors. Based on Social Cognitive Theory, this study examined the relationship between perceived peer support and academic achievement among university students, as well as the mediating roles of emotion regulation and behavioral engagement. Data were collected from 560 undergraduate students from two universities in China using a time-lagged three-wave survey design within one academic semester. Structural equation modeling was used to test the proposed mediation model. The results indicated that perceived peer support was positively associated with academic achievement. Emotion regulation and behavioral engagement each mediated this relationship. In addition, a significant sequential mediation pathway was identified, indicating that perceived peer support was associated with higher levels of emotion regulation, which in turn predicted greater behavioral engagement and subsequently higher academic achievement. These findings highlight a social-emotional-behavioral pathway linking peer support to academic achievement within the environment-person-behavior framework of Social Cognitive Theory. Practically, fostering supportive peer environments and promoting students’ emotion regulation skills may help encourage greater engagement and support students’ academic development.</p>