Folie à deux is uncommon in adults. The most common combinations of patients are mother-child and husband-wife duals whose diagnoses are schizophrenia. Children in such a relationship might be either maltreated or neglected. No Taiwanese childhood-onset case report of folie à deux has been reported. We hereby report on one child's delusion induced by his schizophrenic mother. Case report: A 10-year-old boy gradually developed bizarre and persecutory delusions after his mother had suffered from similar delusions. The boy was hospitalized for accident and self-harm risk while his mother was admitted to another hospital for schizophrenia. After separation of the boy and his mother for ten days, the boy recovered during hospitalization without any medication. This case highlights that separating that child with folie à deux from his psychotic parent and non-pharmacological interventions may be beneficial to childhood-onset folie à deux.