Children with intellectual disabilities placed in residential services face challenges in making their voices heard and expressing their support needs. It is important to understand how these children can be more involved in their support arrangements. This study utilises secondary data from group interviews and child case studies to investigate child involvement in the design and delivery of support, and staff actions concerning support development related to child involvement when a support development programme is realised. The analysis used the theoretical model of Doing to, Doing for, and Doing with to explore the level of involvement in supporting the children. The findings demonstrate that a person-centred support development programme can foster child involvement in residential services across different levels, despite children’s varying capacities. This includes staff understanding of those capacities, which pose challenges to involvement. Organisational support for working methods and competence increases the opportunity for residential staff to give children a voice in co-design and co-delivery, in line with children’s capacity.