Associations between social norms and bullying bystander behaviours have been studied extensively over the years, but the mechanisms by which subjective norms influence bystander behaviours remain unclear. This study is the first to examine whether bystander popularity moderates the association between perceived peer pressure for intervention and Chinese adolescents' bullying bystanding behaviours. The participants were 419 (51.6% male) school students (grade 8-11, age 14-17 years). The results showed positive associations between perceived peer pressure for intervention and active defending behaviours, and negative associations between perceived peer pressure for intervention and passive bystanding behaviours. Further, the results indicated that popularity moderated the association between perceived peer pressure for intervention and active defending behaviours. These findings highlight the importance of considering interactions among subjective norms and individual factors such as popularity when attempting to understand the factors that promote or hinder active defending behaviours. Moreover, the findings shed light on the importance of evidence-based bullying bystander interventions that help recognize these popular students.