Using semi-structured interviews, we examined teachers' understanding of bullying of children in their classes. Although teachers' definitions of bullying included both direct and indirect behaviours, several factors influenced how they characterized and responded to incidents. These factors included whether the teachers viewed an incident as serious or considered a victimized child responsible, whether a child matched their assumptions about victim characteristics and behaviours, and whether they described feeling empathy for a child. The nature of the school environment and organization such as availability of systemic support in addressing bullying incidents were further factors that influenced teachers' awareness and responses.