Children with chronic illnesses are called to undertake complicated processes of adjustment and re-organization in their daily lives; as a result, they could experience several internalizing problems. Symbolic play could be a useful way to cope with these difficulties. The main aim of this paper is to assess pretend play, coping, and psychological symptoms in three groups of school-aged children with pediatric chronic diseases. The study involved 44 Italian school-aged, chronically ill children: 16 with type 1 diabetes mellitus (T1DM), 12 with cystic fibrosis (CF), and 15 with Leukemia. All patients were assessed by the Affect in Play Scale–Brief version (APS-Br), and the Children’s Coping Strategies Checklist–Revision1 (CCSC-R1). Children with T1DM and CF also completed the Separation Anxiety Symptom Inventory for Children (SASI-C) and the Strengths and Difficulties Questionnaire (SDQ)–children’s version. Cohen’s d (effect size) was applied between clinical and normative samples, and it showed a more organized play (APS-BR), but a more negative affect tone, comfort, and frequency of affect expression. Comparing APS-BR and CCSC-R1 rates between the three groups, significant differences were found for all the APS-BR dimensions, except for tone, and for CCSC-R1 seeking understanding. Comparing SASI-C score between T1DM and CF, higher scores were found for children with CF. In the end, correlations between all dimensions highlighted several relationships between play, coping, and adjustment problems for children with T1DM, and relationship between affect play and all variables for children with CF. Symbolic play helps chronically ill children to express emotions; helping them, as well as clinicians, to understand the difficulties caused by chronic conditions, and to cope with them.