Peer victimization in schools is a growing concern in China, linked to increased emotional difficulties and behavioral difficulties. A positive school climate may serve as a protective factor against both peer victimization and its adverse outcomes. This study examined the longitudinal relations between peer victimization, aggression, and school climate by examining self-report survey data collected from 800 3rd to 6th-grade students (M[subscript age]= 9.87 years, SD = 1.15 years) from five elementary schools in China over six months. Path analysis results indicated that peer victimization at Time 1 (T1) significantly predicted aggression at Time 2 (T2), while aggression at T1 did not predict peer victimization at T2. Furthermore, a positive school climate at T1 buffered the positive relation between peer victimization at T1 and aggression at T2. These findings have important implications for peer victimization prevention and school climate promotion in China.