Background Adults’ perceptions of children with disruptive behaviour disorders (DBDs), which usually interfere with socialization and referral of children to mental health services, might differ according to the child's sex. Given the importance of (a) the interactions between these children and their educators, and (b) early identification and referral, the impact of the child's sex on adults’ perceptions is an important factor to consider. Aim To examine the role of gender-related expectations in the identification and referral of childhood DBDs by trainee nursery teachers. Sample One hundred and fifty-eight female trainee nursery teachers (mean age = 20 years) at the Department of Early Childhood Education in Athens. Method Trainee nursery teachers’ perceptions of male and female children with DBDs were explored using a Greek version of the Parental Account of the Causes of Childhood Problems Questionnaire. Eighty-one participants answered questions about a set of disruptive behaviours ascribed to a boy and 77 about the same behaviour ascribed to a girl. Results DBDs ascribed to girls were considered to be no more severe or of greater concern than those ascribed to boys. Judgements of severity were related to concern in the same way for boys and girls. However, DBDs were regarded as less typical for girls than boys. Conclusions The child's sex affected trainee teachers’ judgements of typicality, but not severity, of children's behaviour problems. The implications of this finding for socialization practices and referral attitudes are discussed.