Ehrlichiosis should be considered in the differential diagnosis of any patient with recent fever, pancytopenia, hepatosplenomegaly, and history of tick exposure. We present a previously healthy 5-year-old boy who was referred to the Hematology-Oncology Clinic to consider a bone marrow etiologic process after his pediatrician discovered progressive neutropenia, anemia, thrombocytopenia, and hepatosplenomegaly accompanied by 2 days of fever. Bone marrow aspirate and biopsy were nonrevealing. Because of the history of a recent tick bite, a diagnosis of ehrlichiosis infection was considered and ultimately confirmed by IgG-specific serum testing. The patient's fever was treated symptomatically with acetaminophen, and symptoms resolved on their own without intervention. Ehrlichiosis is a tick-borne infection that occurs throughout the spring and summer, often causing findings that mimic a malignancy or serious hematologic disorder. The diagnosis should be considered in any person living in tick-infested areas and can be confirmed by polymerase chain reaction or serum antibody titers. Treatment with doxycycline can lead to rapid clinical improvement if the diagnosis is made early.