The present study aimed to investigate and compare school principals' and teachers' perceptions regarding online risk behaviours in school-aged children, examining simultaneously the predictive role of their perceived self-efficacy in their perceptions under study. The participants were 237 principals and 295 teachers, mainly from Central Macedonia and Attica, who completed a self-reported online questionnaire. According to the findings, participants declared awareness of students' online risk behaviours. However, compared to teachers, principals to a greater extent felt confident to manage this issue and support school community involvement in the prevention of/intervention in it. Furthermore, principals' self-efficacy in promoting students' learning/ethical behaviours in school and teachers' self-efficacy in managing students' behavioural problems inside a classroom predicted positively their perceptions under study. The findings indicate the necessity of applying differentiated related training programmes for principals and teachers, highlighting simultaneously the importance of their perceived self-efficacy in how they approach the issue studied.