This empirical study examined how subjective norms (SNs) and perceived severity affected teachers' intention to intervene and their intervention behaviors in real-life bullying incidents in primary and secondary schools. A total of 362 teachers who witnessed or were told about bullying incidents participated in this study by completing related questionnaires. Results showed that (a) SNs were positively related to teachers' intervention, and intention to intervene partially mediated the association between SNs and teachers' intervention behaviors in bullying incidents; (b) The mediation effects were moderated by perceived severity, meaning that SNs predicted teachers' intention to intervene positively and significantly only at a low level of perceived severity. These results suggested that higher subjective norms may be more conducive to promoting teachers' intervention in less severe incidents of bullying or increasing the intervention behavior of teachers who do not perceive bullying to be a serious problem. Therefore, future anti-bullying program should focus on improving teachers' anti-bullying norms and scientific perceptions of bullying through regular teacher training and integrating anti-bullying rules and policies into the school climate.