The current study investigated the dynamic reciprocal relationships between adolescents’ school victimization and self-esteem during the first 2 years in secondary schools and how the relationships varied by social support. Participants were 2550 Chinese adolescents (52% males; 48% females) aged 11–16 years (Mage = 12.99 years, SDage = 0.58) who had just entered secondary school and were followed for 2 years. A cross-lagged path analysis was used to examine the reciprocal relationships between school victimization and self-esteem, and a multiple-group analysis was used to examine the moderating roles of peer support and teacher support. The results showed that from the fall semester to the spring semester in Grade 7, adolescents’ victimization predicted subsequent low self-esteem, while from the spring semester in Grade 7 to the fall semester in Grade 8 and from the fall semester in Grade 8 to the spring semester in Grade 8, adolescents’ low self-esteem predicted subsequent victimization. Furthermore, teacher support moderated the relationship between victimization and self-esteem, such that the above negative associations existed only when adolescents’ perceived teacher support was low. However, this protective effect was not found with peer support. The findings highlight the transactional dynamics between school victimization and self-esteem and the protective role of teacher support, which has implications for effectively preventing and intervening school bullying.