Child sexual abuse prevention strategies typically focus on teaching children 'protective behaviours', including telling a 'trusted adult'. However, disclosure rates are low, and we know little about who they tell. We analysed data from over 3400 young people aged 10-18. After viewing hypothetical unsafe scenarios involving either an adult or peer, participants were asked whetherand whomthey would tell someone if such a situation occurred. Most (83.9 per cent) said they would tell someone about concerns involving an adult; fewer (79.3 per cent) would tell if they encountered an unsafe situation with a peer. Across adult and peer scenarios, participants were most likely to say they would approach their mother (about concerning behaviour of an adult, 68.7 per cent; or a peer, 63.1 per cent), a friend (64.4; 57.9 per cent) or their father (52.2; 48.9 per cent). Those most likely to tell a friend were girls and older children. Children in out-of-home care and community welfare organisations were less likely to tell someone about concerning behaviour from a peer/friend than in other organisational contexts. Although organisations must train staff in supporting young people who raise concerns or make disclosures, it is vital to consider the role of parents and other young people in hearing about concerns and building their capacity to respond appropriately.