Background Sexual development plays a vital part in young people's emotional adjustment. Method This study compared the sexual understanding of 30 adolescents with mild intellectual disabilities (ID) and 30 non‐disabled adolescents, along with their reports of where they obtained sexual information, and the nature of their social networks and support. Results As expected, the non‐disabled young people had superior levels of knowledge. However, an interaction was found between group and gender. The non‐disabled young women had a better grasp of sexual matters than men, whereas the opposite was the case for those with ID. The non‐disabled young people reported more formal and informal sources of sexual information and described larger social networks than those with ID. Conclusions These findings highlight the need to tackle the barriers to sexual knowledge faced by young people with ID, and the need to take account of the broader social context of their lives when doing so. This includes the attitudes to the developing sexuality of young women with ID in particular.