Oncology patients are a unique patient population in the emergency department (ED). Malignancy and associated surgical, chemotherapeutic, or radiation therapies put them at an increased risk for infection. The most ominous development is neutropenic fever, which happens often and may not present with signs or symptoms other than fever. A broad differential diagnosis is essential when considering infectious disease pathology in both neutropenic and non-neutropenic oncology patients in the ED.