This study aims to provide a new perspective on the relationship between perceived teacher emotional support and externalizing problem behaviors among adolescents. Some studies have focused on the relationship between perceived teacher emotional support and externalizing problem behaviors. However, research on the underlying mechanism is still insufficient. Additionally, peer relationship, mental health, and parental knowledge have been ignored as a crucial factors. Altogether, 7101 Chinese rural adolescents aged 13-19 years completed an anonymous self-report questionnaire. The results show that: (1) perceived teacher emotional support has a protective effect against the development of externalizing problem behaviors; (2) peer relationship and mental health both have a mediating role in the relationship between perceived teacher emotional support and externalizing problem behaviors in rural adolescents; (3) perceived teacher emotional support can indirectly affect externalizing problem behaviors through the chain mediation of peer relationship and mental health; (4) parental knowledge has the potential to moderate the indirect impact by diminishing the association between perceived teacher emotional support and externalizing problem behaviors; and (5) the impact of perceived teacher emotional support on externalizing problem behaviors has significant gender differences. The protective impact was greater on boys than on girls. In relation to these findings, this study has discussed the possible reasons and made some practical suggestions to improve teacher emotional support among rural adolescents.