Research on bullying underlines the role of significant adults: the way teachers and parents respond to offline bullying has the potential to reduce bullying behaviours, but whether they have an influence on cyberbullying is unknown. This study delves into what effects parent and teacher responses to offline bullying have on cyberbullying. The sample was composed of 1.406 middle and high school students (F = 41%; M[subscript age] = 13.1, SD = 1.4). We developed ad hoc measures to simultaneously estimate teacher and parent responses to offline bullying, i.e. non-intervention, disciplinary methods and supportive/relational interventions. Using a SEM model, we found that parents' supportive/relational interventions are associated with lower levels of cyberbullying behaviours. At the same time, teachers' non-intervention in offline bullying episodes was associated with higher involvement in cyberbullying. Findings highlight the critical and complementary role that parents and teachers play in preventing cyberbullying.