BACKGROUND Hemophagocytic lymphohistiocytosis (HLH) is a rare life-threatening systemic hyperinflammatory condition. Most adult HLH cases are secondary to infection, malignancy, and rheumatic diseases. Epstein-Barr virus (EBV) infection is the most frequent cause of infection-induced HLH. Early treatment with dexamethasone, etoposide, and cyclosporine is generally recommended for adult patients with HLH. However, this treatment regimen was established based on pediatric clinical trial data; thus, its efficacy and validity in adults remain unclear. Because little is known about the disease course of untreated adult EBV-associated HLH (EBV-HLH), we report a case of an adult patient who recovered from EBV-HLH spontaneously without specific treatment and discuss potential treatment strategies. CASE REPORT A 34-year-old man presented to the emergency department with a 7-day history of fever, headache, and sore throat. The main laboratory test abnormalities were elevated liver enzymes, hyperbilirubinemia, hypertriglyceridemia, and hyperferritinemia. Serologic tests confirmed acute primary EBV infection. He was diagnosed with EBV-HLH based on the HLH-2004 diagnostic criteria and the HLH probability calculator (HScore). Because he was clinically stable, we did not initiate immunosuppressive/cytotoxic treatment targeting HLH. High-grade fever persisted, but the abnormalities in his laboratory data improved spontaneously, and he did not develop major organ failure. His fever resolved on day 29 without HLH-specific treatment. CONCLUSIONS In clinically stable adult patients with EBV-HLH without major organ failure, it might be an acceptable alternative to observe the patient for several weeks before initiating HLH-specific treatment. Further research is required to better predict the subset of patients who can be safely observed without treatment.