Mucormycosis is an aggressive and often fatal infection, despite conventional methods of treatment, which predominantly affects immunocompromised patients. This report describes an outbreak of rhinocerebral mucormycosis in a university hospital paediatric oncology department secondary to water damage in a linen store and parents' shower room. The source of the outbreak was successfully determined using simple environmental sampling techniques. Sampling allowed timely and successful implementation of infection control measures to contain the source and protect patients. Two cases were treated with posaconazole and made a complete recovery, with no discernible impact on the management of their cancer. Fifteen other children identified as having a high risk of developing infection were given posaconazole prophylaxis. None of the children, including one that was only five years old, experienced any adverse events from taking posaconazole.