Invasive fungal infections may cause morbidity and mortality in pediatric patients with hematologic and oncologic malignancies treated with intensive protocols. We present a case of mucormycosis in an 8-year-old boy with acute lymphoblastic leukemia. In our patient, the suspicion for an oculoorbital and paranasal infection only due to mild pain in the orbital area without any abnormal pathologic findings in the ophthalmologic and otolaryngologic examination, led us to an early diagnosis. Despite the use of antifungal therapy, the lesion persisted and fever subsided after surgical drainage of the periorbital abscess. Antifungal treatment continued during chemotherapy. He has been in remission for four years. Mucormycosis should be in the differential diagnosis in infections in children with cancer, especially leukemia, according to clinical and radiologic findings. A high degree of suspicion and prompt systemic empirical antifungal therapy, as well as surgical debridement, are crucial for the survival of patients. Beside antifungals, early surgery plays an important role in patients with mucormycosis.