Non-steroidal anti-inflammatory drugs are the conventional treatment for pericarditis. However, some patients will still suffer from persistence pericardial effusion despite exhausting all conventional management options. A 4-year-old girl with idiopathic pericardial effusion who did not respond to 2 months of conventional therapy had complete resolution of effusion within 5 days, with no recurrence after administration of intrapericardial steroids. As far as we know, this is the first published paediatric case who has shown a similar outcome to that seen in adult studies.