<p>Given its vicious cycle of victimization, early life adversity (ELA) in childhood may be associated with peer victimization during adolescence. Both ELA and peer victimization have been suggested to be major risk factors for depression. Volumetric alterations in the hippocampus implicated in stress sensitivity have been reported in individuals with ELA and peer victimization. This cross-sectional study examined the moderating role of hippocampal volume in the association between ELA and peer victimization in adolescents with major depressive disorder (MDD). The sample included 78 adolescents with MDD (age M (SD) = 14.92 (1.54) years, 56 females). The Early Trauma Inventory-Short Form and Peer Victimization Scale were used to assess participants’ ELA and peer victimization, respectively. High-resolution structural T1 images were obtained using a Siemens 3T magnetic resonance scanner. Whole hippocampal volumes were segmented and calculated using the FreeSurfer 6.0. Correlation and moderation analyses were also performed. Emotional abuse, a type of ELA, was significantly correlated with peer victimization after controlling for age and sex. The association between emotional abuse and peer victimization was moderated by bilateral hippocampal volume in adolescents with MDD after controlling for age, sex, and intracranial volume. Additionally, the association between emotional abuse and peer victimization was stronger when the bilateral hippocampal volumes were larger. Our findings partially supported the concept of a vicious cycle of victimization, which may be a critical aspect of depression in adolescents. Furthermore, the moderation results suggested that hippocampal volume plays an important role in the victimization cycle in adolescents with MDD.</p>