We describe an outbreak of mucormycosis in a pediatric oncology hospital during December 2010 and the measures taken to stop it. The outbreak began with two consecutive cases of laboratory‐documented mucormycosis infections within 1 week. Investigations to track the source were conducted immediately. Air plate cultures from machines and ducts supplying patients’ rooms revealed the growth of Rhizomucor. Of five affected patients, all had acute leukemia and three were histopathologically proven. All patients were treated with liposomal amphotericin B after mucormycosis was diagnosed. Posaconazole was used as a secondary prophylaxis in one case. Three patients died. Pediatr Blood Cancer © 2015 Wiley Periodicals, Inc.