While the historical benefits of hydrogen peroxide on wounds and wound healing have recently been questioned, physicians have started to explore its other potential medicinal benefits. We present a case of a 14-year-old girl who presented to our urology unit with macroscopic haematuria and clot retention. Ultrasonography confirmed a large organised intravesical blood clot. Despite numerous attempts, manual bladder irrigation was unsuccessful and caused significant discomfort to the patient. Her clot retention was relieved after 4 irrigation cycles with a 3 % hydrogen peroxide solution. She experienced no complications or side effects post intravesical instillation of hydrogen peroxide.