In adults with neuromuscular conditions illness perceptions show a strong relation with QoL. For young patients, illness perceptions are shaped through interaction with their parents. A shared perception between child and parent may benefit the child's QoL. This study investigated agreement in illness perceptions of children with Spinal Muscular Atrophy (SMA) and their parents, the association between the child's illness perceptions and QoL, and the relation between child-parent agreement in illness perceptions and the child's QoL. Twenty-six children and their parents completed the Brief Illness Perception Questionnaire (BIPQ) and the Kidscreen-52 QoL questionnaire (children only). Correspondence between children's and parents' illness perceptions was low. Generally, parents held more negative illness perceptions about SMA. Whereas children's illness perceptions were related to QoL, no clear association was found between agreement in illness perceptions and children's QoL. Therefore, to understand and improve QoL, healthcare professionals should discuss children's own illness perceptions during consultations.