The incidence of type 1 diabetes (T1D) in young children is increasing markedly however young children have been overlooked in paediatric adherence research despite the unique challenges their care presents. We investigated the relation between maternal communication style and adherence to the dietary regimen in 40 children with T1D, aged 2-8 years, and their mothers. Mothers completed measures of children's sugar consumption, parent-child communication quality, and child psychological functioning. Mothers and children engaged in a videotaped problem-solving task related to the dietary regimen, with maternal utterances analysed for behavioural control style (e.g., commands versus suggestions) and cognitive complexity (e.g., provision of labels versus questions). Maternal communications which engaged children, behaviourally and cognitively, in the task were associated with better adherence, medical, communication quality, and child adjustment outcomes. We conclude that adherence and health (medical and psychological) are optimized when young children are given opportunities to participate in their care.