Background: Illness perceptions comprise assumptions about symptoms, timeline, consequences, controllability, and emotional responses of an illness. Recent evidence shows that illness perceptions are associated with coping and well-being. Until now, assessment is based on parental report only, since no instrument for the direct assessment of children is available. Objectives: Development of a puppet interview for the age-appropriate assessment of illness perceptions in children up to the age of 4 years. Recommendations for the application (including indications and contraindications) and assessment of psychometric properties. Materials and methods: The puppet interview was developed based on the Illness Perception Questionnaire (IPQ-R) and the Berkeley Puppet Interview and examined in two samples of patient–parent dyads (n = 11 und n = 64). Results: The puppet interview is applicable (comprehensible, useful) in acute treatment and follow-up care. Illness perceptions may vary in different treatment phases. We saw confirming intercorrelation of scales (chronicity – consequences: r = 0.690, p ≤ 0.05) and adequate psychometric properties (construct validity: chronicity – internal control: r = −0.711, p ≤ 0.05, internal consistency). Some children even discussed potential coping strategies with the puppets. Conclusion: Parental report can be complemented by a self-report measure of illness perceptions in affected children aged 4 years and older. This will allow for the further adaptation of medical and psychosocial treatment.