Paediatric supraventricular tachycardia (SVT) is a common arrhythmia of great clinical significance. If not treated promptly, it can cause heart failure and cardiogenic shock. Depending on the patient’s condition SVT treatment involves vagal manoeuvres, pharmacological or direct current cardioversion. The goal of acute SVT management is to immediately convert SVT to normal sinus rhythm (NSR) and prevent its recurrence. Adenosine is recommended as first-line treatment for stable SVT by the European Resuscitation Council (ERC) and American Heart Association (AHA) guidelines when vagal manoeuvres have proven ineffective. ERC and AHA guidelines recommend the intravenous route of administration. Intraosseous (IO) administration technique is also possible, but still relatively unknown. The aim of this paper is to describe a 3.5-year old child with SVT which was converted to NSR following IO administration of adenosine. Successful conversion was achieved in the second attempt with the adenosine dose. In the described case, there was no recurrence of SVT.