The purpose of this study was to examine the reciprocal relationships between students' engagement and their relationships with teachers and peers in the context of Chinese educational reform. The participants were 628 7th-grade students from a public secondary school in Beijing. All of the students completed self-reported student engagement, teacher--student relationships and peer relationships measures at three time points within 3 years (at the end of the 7th grade, 8th grade and 9th grade). Through cross-lagged models, this study found that prior-year teacher--student relationships could predict the cognitive component of student engagement only in the 9th grade. However, higher levels of behavioural, emotional and cognitive engagement predicted subsequent higher-quality teacher-student relationships from the 7th to the 9th grades. Moreover, previous peer relationships predicted student behavioural and cognitive engagement in the 8th grade and emotional engagement in the 9th grade. Prior-year behavioural, emotional and cognitive engagement predicted peer relationships in the 8th grade, but the prediction was significant only for the influence of behavioural engagement on peer relationships for older students between the 8th grade and the 9th grade. Implications for supportive interpersonal relationships with teachers and peers that facilitate student engagement are discussed.