This chapter considers the experiential expertise of children and young people through a case study of the children’s telephone helpline, ChildLine UK. ChildLine was launched in 1986 as the first nationwide telephone helpline for “children in trouble or danger”. Initially offering a service to listen to children’s needs and problems, it developed as a lobbying body for policy change around children’s welfare. Reading organisational literature alongside evidence of ChildLine’s reception amongst policy-makers, practitioners, and children, the chapter offers an innovative methodological approach to examine the communication and translation of experiential expertise about children’s wellbeing. It looks both at the representation of children as experiential experts by ChildLine, exploring the presentational strategies used within organisational publications to harness young people’s experiential expertise, and how the helpline claimed professional expertise in children’s wellbeing. This work was not achieved without resistance, however, and the final section of the chapter discusses evidence of children cutting across the organisation’s goals to represent children’s experience and experiential expertise. Children’s subversive acts, it is argued, show young people engaging with the helpline in order to articulate alternative ideas about the usefulness of the service within their own logics of fairness and wellbeing, which might be different to ChildLine’s.